Learn past modals of deduction with this engaging grammar worksheet featuring examples and exercises.

Let’s go step by step to solve each sentence using the correct past modal of deduction.

We are told to use:
- “must have” + past participle → for 90% sure (very likely)
- “may have” or “might have” + past participle → for 50% possible (not sure)
- “can’t have” or “couldn’t have” + past participle → for impossible (definitely not)

Now, let’s look at each sentence:

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1. Your mother __________ (be) a great cook. Your siblings were fighting over her old cooking book.

→ Evidence: Siblings were fighting over her old cooking book. That suggests she was really good — people don’t fight over something unless it’s valuable or special. So we’re *pretty sure* she was a great cook.

→ Use: must have been

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2. I’m not sure yet, but I guess Gracia __________ (eat) my cookies. Her smile was suspicious.

→ Evidence: “I’m not sure yet” and “her smile was suspicious” — this is just a guess, not certain. So it’s only *possible*, not definite.

→ Use: may have eaten (or “might have eaten” — both are acceptable; we’ll pick “may have eaten” as it’s listed first in instructions)

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3. Denis __________ (get) lost. He knows this neighborhood like the back of his hand!

→ Evidence: He knows the neighborhood very well (“like the back of his hand”) — so it’s *impossible* that he got lost.

→ Use: can’t have gotten (or “couldn’t have gotten” — again, both work; we’ll use “can’t have gotten” as it’s listed first)

Note: In American English, “gotten” is the past participle of “get”. In British English, it’s often “got”, but since the verb given is “(get)”, and we need past participle, “gotten” is correct here for standard usage in this context.

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4. I can see that Carol is still mad at me. She __________ (leave) my bags outside the house. I will have to apologize again!

→ Evidence: She left my bags outside — and I know she’s still mad. This action makes sense if she’s angry. It’s very likely she did it on purpose because she’s upset. So we’re *almost sure*.

→ Use: must have left

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✔ All answers checked against evidence and rules.

Final Answer:
1. must have been
2. may have eaten
3. can’t have gotten
4. must have left