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Science (086) — AI-generated practice question

AI-generated practice question — model-generated for extra practice, not a previous-year CBSE board question.

Q1. [1] deep exam-ready
Assertion (A): Desert plants take in carbon dioxide at night rather than during the day. Reason (R): Opening stomata during the day in a desert would cause excessive water loss, so CO₂ is fixed at night and stored as an intermediate for use during daytime photosynthesis. (A) Both A and R are true and R is the correct explanation of A. (B) Both A and R are true but R is not the correct explanation of A. (C) A is true but R is false. (D) A is false but R is true.
  1. A Both A and R are true and R is the correct explanation of A.
  2. B Both A and R are true but R is not the correct explanation of A.
  3. C A is true but R is false.
  4. D A is false but R is true.
Generated by claude-sonnet-4-6 · 2026-06-26 00:59 · grounding rag
Model Answer

(A) Both A and R are true and R is the correct explanation of A.

Desert plants take in CO₂ at night to avoid water loss through open stomata in the hot daytime, storing it as an intermediate that is used for photosynthesis during the day when sunlight is available.

Source: Life Processes, Chapter 5, Section 5.2.1 – Autotrophic Nutrition

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Explanation

The textbook explicitly states: "desert plants take up carbon dioxide at night and prepare an intermediate which is acted upon by the energy absorbed by the chlorophyll during the day." It also explains that plants close stomata to prevent water loss when CO₂ is not needed. Both statements are factually correct, and R directly explains the adaptive reason behind A, making option (A) the right choice.

Previous-year CBSE Grade 10 board exam questions, organised by subject and chapter, each with a model answer — free to read and print.