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Assertion (A): In reptiles… (Class 10 Science 2025, Q19)

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ScienceCBSE Class 10 · Board exam 2025, set 31/4/1 · 1 mark · Assertion-reason

CBSE Class 10 Science 2025: question 19

Set in the CBSE Class 10 board exam of 2025, paper 31/4/1, section A, question 19, for 1 mark. Try it first; the hints and our step-by-step solution are below.

Q19 · 1 mark · Assertion-reasonCompetency-basedHeredity

Assertion (A): In reptiles, the temperature at which the fertilized eggs are kept decides the sex of the offsprings.

Reason (R): Sex is not genetically determined in some animals.

  1. (A)Both, Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
  2. (B)Both, Assertion (A) and Reason (R) are true, and Reason (R) is not the correct explanation of Assertion (A).
  3. (C)Assertion (A) is true, but Reason (R) is false.
  4. (D)Assertion (A) is false, but Reason (R) is true.

Source: official question paper from cbse.gov.in (PDF). See it in the full 2025 board paper, set 31/4/1.

Hints

Open one hint at a time and try again before the next.

Hint 1

Recall the example of turtles from NCERT.

Hint 2

Does R give the reason for A?

Step-by-step solution

Each step shows the marks it earns, as an examiner would award them. Checked by an independent re-solve from the question paper.

  1. Both statements are true: in some reptiles, such as turtles, the incubation temperature of the eggs decides the sex of the offspring.

  2. This happens because sex is not genetically determined in these animals, so R correctly explains A. Option (A).

    1 mark

Answer: (A)

Where the marks are

  • Both true, R explains A (1 mark)

Revise the chapter

Practise this chapterBoard-style questions from Heredity, one at a time, marked against the answer key and marking points.Back to the full paper2025 board paper, set 31/4/1: every question, by section.

The question is transcribed from the official paper; figures are described in words. The solution, hints and chapter tag are ours. Spotted an error? Write tosupport@questionbuddy.in.