The prolonged illness left him totally . . . . . . .

The correct answer is A. enervated.

Enervated means to be weakened or exhausted, especially by illness or exertion. In this case, the prolonged illness left the man totally weakened and exhausted.

The other options are incorrect because they do not accurately describe the man’s condition.

• Invalid means a person who is permanently disabled or sick. The man in the question is not permanently disabled or sick, he is simply weakened by his illness.
• Indisposed means not feeling well, but not seriously ill. The man in the question is seriously ill, so he is not simply indisposed.
• Healthy means free from illness or injury. The man in the question is not healthy, he is ill.