Unit 6 · Identifying Sufficient Information

Warm Winter Confirmed — Are Possums Innocent?

Lesson 11 of 12

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Mr Murray confirmed that a warmer-than-normal winter explains why only 5 of his 20 crocus plants grew — so he concluded the possums are innocent. But he started with two possible causes. Does confirming one cause automatically rule out the other? This is the most common single-cause trap in OC TS flaw questions.

Chapters

0:00Introduction
0:22The Question
1:22Step 1: Identify Mr Murray's reasoning structure
1:48Step 2: Why confirming one cause is not enough
2:14Step 3: Test each option
2:47Correct answer

Question

Last winter, Mr Murray planted twenty crocus plants but only five of them grew. After some research, Mr Murray found that there were two possible reasons for this:
- The winter may have been too warm, as crocuses need cold weather to grow.
- Possums may have dug up the crocus plants for food before they could fully grow.

Mr Murray: "I checked the weather reports and the average temperature during the winter was indeed higher than normal. That must be the reason why so many of the crocuses didn’t grow, so I shouldn’t blame the possums."

Which one of the following sentences shows that Mr Murray has made a mistake?

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