Choose the word that means the opposite of the highlighted word in the…

CONCEPT

An antonym question asks for the word whose meaning directly reverses the highlighted word's sense — not a related word or a synonym. First pin down the exact sense the highlighted word carries in this sentence, then match that sense's precise opposite.

APPLICATION

Here, "slacken" means to make something slower, looser, or less active; in this sentence it means to reduce the pace of work. The direct opposite of reducing pace is increasing it, i.e. to speed up or hasten. This is exactly what "accelerate" means, so it reverses "slacken" in this context.

CROSS-CHECK / CONTRAST

Checking the other options confirms none of them reverse the sense of slowing down:

• "monitor" means to watch or keep track of an activity; it describes observation, not a change in speed, so it does not oppose "slacken".

• "supervise" means to oversee or direct work, again a managerial role, not a reversal of pace.

• "control" means to regulate or restrain the pace; this sits closer to moderating/slowing than to speeding up, so it does not reverse "slacken" either.

Result: since only one option reverses the "reduce pace" sense of "slacken" into "increase pace," that option is the correct antonym.