A student recorded only the results that supported the hypothesis. This is an example of which problem?

Correct answer: Confirmation bias

The direct answer is C, confirmation bias. A fair investigation requires recording every relevant result, including results that do not support the hypothesis. If a student chooses only favourable results, the evidence becomes incomplete and the conclusion is likely to be unfair. That habit is called confirmation bias: accepting information that agrees with an existing belief and ignoring information that disagrees. Option A, random error, is an unpredictable variation in measurements, not selective recording. Option B, measurement limit, is the smallest amount an instrument can reliably show and does not describe choosing results. Option C is correct because the student selected evidence to confirm the hypothesis. Option D, a controlled test, is a fair design in which important conditions are kept constant; it is the opposite of this problem. Exam reminder: never hide an unexpected result; record it, check it, and discuss it honestly.