Assertion and Reason — CBSE MCQ Format

Format of Assertion and Reason Questions: • Assertion (A): a statement that may be true or false • Reason (R): another statement that may be true or false and may or may not explain A

Standard Four Options (CBSE): (a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A). (b) Both Assertion (A) and Reason (R) are true, but Reason (R) is NOT the correct explanation of Assertion (A). (c) Assertion (A) is true, but Reason (R) is false. (d) Assertion (A) is false, but Reason (R) is true.

Note: Some papers include a 5th option: (e) Both Assertion (A) and Reason (R) are false.

How to Approach A&R Questions: Step 1: Evaluate Assertion (A) — Is it true or false? Step 2: Evaluate Reason (R) — Is it true or false? Step 3: If both are true — does R explain A? • If yes → Option (a) • If no → Option (b) Step 4: If only A is true → Option (c) Step 5: If only R is true → Option (d)

Decision Tree: • A true + R true + R explains A → (a) • A true + R true + R does NOT explain A → (b) • A true + R false → (c) • A false + R true → (d) • A false + R false → (e) [if this option exists]

Examples:

Example 1 (Science — Biology): • A: Mitochondria is called the powerhouse of the cell. • R: Mitochondria produces ATP through cellular respiration. • Answer: (a) — Both true; R correctly explains A.

Example 2 (Science — Chemistry): • A: Noble gases are highly reactive. • R: Noble gases have a completely filled outermost electron shell. • Answer: (d) — A is false (noble gases are INert); R is true.

Example 3 (Social Science): • A: India is a federal country. • R: India has two levels of government — central and state. • Answer: (b) — Both true; but two levels of government alone doesn't fully explain federalism.

Example 4 (Science — Physics): • A: Sound cannot travel in vacuum. • R: Sound is a mechanical wave that requires a medium. • Answer: (a) — Both true; R correctly explains A.

Common Mistakes: • Reading only A and choosing (a) without checking R • Confusing 'R explains A' with 'R is related to A' • Not verifying both statements independently

Marks: Usually 1 mark each in CBSE board exams