Directions: For question number 24, two statements are given, one labelled as Assertion (A) and the other is labelled as Reason (R). Select the correct answer from the codes given below. Assertion (A): Carbon shares its valence electrons with other atoms of carbon or with atoms of other elements. Reason (R): The shared electrons belong to the outermost shells of both the atoms and lead to both atoms attaining the noble gas configuration.

Assertion (A) is true. The NCERT chapter explicitly states: 'Carbon overcomes this problem by sharing its valence electrons with other atoms of carbon or with atoms of other elements.' Since carbon has four valence electrons, it cannot easily form $\mathrm{C^{4+}}$ or $\mathrm{C^{4-}}$ ions (losing/gaining 4 electrons requires too much energy or is unstable for a nucleus with only 6 protons), so it shares electrons instead, forming covalent bonds with other carbon atoms or with atoms of elements like hydrogen, oxygen, nitrogen, sulphur and chlorine.

Reason (R) is true. The chapter states: 'The shared electrons "belong" to the outermost shells of both the atoms and lead to both atoms attaining the noble gas configuration.' This is exactly why sharing (rather than transfer) of electrons is favourable for carbon — both bonded atoms count the shared pair towards their own outer shell, letting each attain a stable, filled valence shell (e.g. duplet for H, octet for C, N, O, Cl) without the energy cost of full electron transfer.

R correctly explains A: A describes that carbon shares electrons; R explains why this sharing is effective — because the shared pair belongs to both atoms' outer shells simultaneously, satisfying noble gas configuration for both without ionisation. This is a direct cause-and-effect link, making option A correct.

Why other options are wrong:

• (B) is wrong because R is not merely a coincidentally true but unrelated statement — it is precisely the mechanism/reasoning that explains why A occurs.
• (C) is wrong because R is factually true as per the text, not false.
• (D) is wrong because A is factually true as per the text, not false.