• Skip to primary navigation
  • Skip to main content
  • Skip to primary sidebar
Home of English Grammar
  • Home
  • Course
  • Exercises
  • Grammar Rules
  • Matches
  • Posts
  • Tools
    • Grammar Checker
    • Very Replacer
    • Word Counter
  • Vocabulary Lists
  • Archives
    • Social Media Posts
    • Writing Guides
  • Join free

Advanced Deduction and Speculation Exercise

March 14, 2026 C2pdf

Complete the 12 sentences below. Choose the best answer for each one. Some sentences have two correct answers. Choose both.

Progress 0 of 12 answered
1Given the scorch marks around the socket, the fire ............... started with an electrical fault rather than a candle.
Wrong!
The clear evidence makes "must have" the best choice for a strong past deduction.
2He keeps checking his phone and smiling; he ............... heard some good news, but I'm not sure.
Wrong!
The phrase "may have" shows a possible past explanation without making it certain.
3If the meeting ended at six, she lives two hours away, and it is only seven, she ............... be home by now.
Wrong!
The modal "can't" shows that being home now is impossible from the timeline.
4The lights are off, so they ............... be asleep, or they might just be out.
Wrong!
The modal "could" expresses a reasonable possibility rather than certainty.
5He ............... be serious, because he just offered to pay in Monopoly money.
Wrong!
The modal "can't" expresses disbelief about a present situation.
6She ............... taken the earlier train, because her ticket is stamped 07.12.
Wrong!
The strong evidence in the ticket stamp supports the past deduction "must have".
7If the server logs are accurate and every login came from an external IP address, the breach ............... come from inside the company.
Wrong!
The phrase "can't have" rules out a past possibility based on the evidence.
8Judging by the silence in the room, his joke ............... landed the way he expected.
Wrong!
The phrase "can't have" makes a negative past deduction from the room's silence.
9With that level of detail in her story, she ............... making it up on the spot.
Wrong!
The phrase "can't be" gives a strong negative deduction about the present action.
10He left without his coat in midwinter, so he ............... been in a rush.
Wrong!
The phrase "must have" gives a strong past deduction from clear evidence.
11If she really wanted to avoid attention, she ............... worn such a bright red suit.
Wrong!
The phrase "wouldn't have" fits a past hypothetical inconsistency.
12The report is unsigned, so it ............... be a draft, but I would need to check with the author.
Select 2 answers.
Wrong!
Both "might" and "could" express plausible speculation without too much certainty.

Exercise complete

0/ out of 12 correct answers
Challenge a friend
More Exercises →

Answers

  1. Given the scorch marks around the socket, the fire must have started with an electrical fault rather than a candle.
  2. He keeps checking his phone and smiling; he may have heard some good news, but I’m not sure.
  3. If the meeting ended at six, she lives two hours away, and it is only seven, she can’t be home by now.
  4. The lights are off, so they could be asleep, or they might just be out.
  5. He can’t be serious, because he just offered to pay in Monopoly money.
  6. She must have taken the earlier train, because her ticket is stamped 07.12.
  7. If the server logs are accurate and every login came from an external IP address, the breach can’t have come from inside the company.
  8. Judging by the silence in the room, his joke can’t have landed the way he expected.
  9. With that level of detail in her story, she can’t be making it up on the spot.
  10. He left without his coat in midwinter, so he must have been in a rush.
  11. If she really wanted to avoid attention, she wouldn’t have worn such a bright red suit.
  12. The report is unsigned, so it might / could be a draft, but I would need to check with the author.

Improve your English grammar, vocabulary and writing

We take you step by step from beginner to advanced, even if you struggled with English at school or have always had trouble remembering the rules.

  • 10 modules, 105 lessons and 688 questions
  • Just log in and learn anytime and anywhere
  • Your progress is saved in your account
  • Download the 2027 Grammar Guide (PDF)

Related lesson in the course Possibility and deduction: might, may, must and can’t Module 05: Modals & conditions · Lesson 4

Join free

Already have an account? Sign in

See what’s in the course

Primary Sidebar

2.4M761.4K165.8K

Free 2027 Grammar Guide

  • Download Grammar Guide (PDF)
  • Online grammar course, A1 to C2
  • Weekly exercises and vocabulary
  • Join over 3 million English learners

We respect your privacy. Unsubscribe anytime.

Already have an account? Sign in

Grammar Checker - Try Now

Latest Posts

  • 100 Best Synonyms for “Spontaneous” October 22, 2026
  • Critical Discussion Error Correction Exercise October 22, 2026
  • 100 Best Synonyms for “Cheerless” October 22, 2026
  • 100 Best Synonyms for “Prophecy” October 22, 2026
  • 100 Best Synonyms for “Spirit” October 22, 2026
  • 100 Best Synonyms for “Distinct” October 22, 2026
  • Comprise, consist of, include, compose, constitute, and make up: How to choose October 22, 2026
  • Describing People Vocabulary Exercise October 22, 2026
  • 100 Best Synonyms for “Properties” October 22, 2026
  • 100 Best Synonyms for “Changeable” October 22, 2026
Home of English Grammar

Free English grammar exercises, rules and vocabulary lists, with new exercises every week. Join the leading English grammar site with over 3 million followers.

Join free

Learn

  • Exercises
  • Matches
  • Grammar rules
  • Vocabulary lists
  • Writing guides
  • Online tools

More

  • Top social media posts
  • Various posts
  • Contact

Account

  • Join free
  • Grammar Course
  • Free grammar guide (PDF)

Copyright © 2026 EnglishGrammar.org

  • Disclaimer
  • Privacy policy
  • Terms
  • Sitemap