Select the most appropriate ANTONYM of the highlighted word
The worker is known to exert himself a lot.

The correct answer is relax.

Explanation:
The word "exert" means to put oneself to great effort, strain, or physical/mental labor (e.g., working very hard or applying pressure/force).

Let us analyze the meaning of all the given options:
1. crouch: To adopt a position where the knees are bent and the upper body is brought forward and down.
2. emerge: To move out of or away from something and come into view.
3. relax: To rest, unwind, or refrain from physical/mental effort and exertion. This is the exact opposite (antonym) of exerting oneself.
4. stress: To subject to pressure or exertion, which is similar in context to exerting oneself rather than opposite.

Therefore, the most appropriate antonym for "exert" is relax.