Replace the question mark (?) with appropriate word from the following: Cruel : Kind :: Lethargy :?

The pair Cruel : Kind is a pair of opposites, so the blank needs the opposite of Lethargy. Lethargy means sluggishness, a lack of energy or drive. Its direct antonym is Alertness, the state of being watchful, quick and energetic. So the answer is B.

• A) Sharpness is close to alertness in meaning, which is why it tempts, but sharpness refers to keenness or an edge, not the direct opposite of sluggishness.
• C) Interest is wrong because lethargy is itself a lack of interest. Choosing it means you are matching a definition rather than reading the relation of opposites.
• D) Sherwdness is not a valid English word. It is a misprint and cannot be the answer.

The core concept is the antonym analogy: identify the relation between the first pair, then find the word that stands in the same relation to the third. In Mains, precise vocabulary and tone matter in essays and precis writing, and this kind of word-pair reasoning builds that control.

Trap: choosing Interest because lethargy is described as a lack of interest. Always check the relation as opposition, not as a definition link.