Answer : 1. "faultlessly"
Explanation :

The most appropriate adverb to fill in the blank would be "clearly."

So, the sentence would be: "They supplied the required human resources."

Solution:

"Faultlessly" doesn't fit the context because it refers to doing something without making mistakes, which may not necessarily apply to supplying human resources.

"Heavy" is an adjective, not an adverb, and it doesn't make sense in the context of supplying human resources.

"Clear" is an adjective, not an adverb, and it doesn't make sense in the context of describing how human resources were supplied.

"Able" is an adjective, not an adverb, and it doesn't fit the context of describing how human resources were supplied.