Select the most appropriate collocating word to fill in the blank.

I listened to him with ________ attention.

rapt

The most appropriate collocating word to fill in the blank is rapt.

The word "rapt" means "deeply engrossed or absorbed". It is the most appropriate option in this context because it conveys the idea of how focused and attentive the speaker was when listening to the other person.

The other options do not make sense in the context of the sentence.

• "Hefty" means "large and heavy". It does not make sense to say that someone listened to someone else with hefty attention.
• "Massive" means "very large". It does not make sense to say that someone listened to someone else with massive attention.
• "Vast" means "very large or extensive". It does not make sense to say that someone listened to someone else with vast attention.