Q.

Correct answer: (a) Both (A) and (R) are true and (R) is the correct explanation of (A).

Assertion (A): The acetate ion (CH3COO⁻) is less basic than the methoxide ion (CH3O⁻).
This is true because the acetate ion is resonance-stabilized. Resonance stabilization spreads out the negative charge over two oxygen atoms, making the acetate ion less likely to donate electrons (i.e., less basic).

Reason (R): Acetate ion is resonance stabilized, while methoxide ion doesn’t show resonance.
This is also true. The negative charge on the acetate ion is delocalized due to resonance, whereas the negative charge on methoxide ion is localized on a single oxygen atom.

Conclusion: Both (A) and (R) are true, and (R) provides the correct explanation for why acetate ion is less basic than methoxide ion.