Most children are __ playing games and collecting things.

• A. fond of
• B. keen on
• C. interested in
• D. crazy about

Answer: (A)

Expressing liking for an activity with the right collocation is what's tested here. The phrase fond of means to like something or have a warm liking for it, and it fits smoothly with activities described by -ing forms. Saying someone is fond of playing games and collecting things conveys a general, gentle liking rather than a strong emotion or mere interest. The gerund forms after fond of are natural: playing games and collecting things.

Keen on can also express liking, but it often sounds a bit more energetic or informal and isn’t as neutral for a broad statement about children. Interested in would work, but it’s a more neutral, less affectionate nuance. Crazy about is quite informal and implies extreme enthusiasm, which is stronger than what “most children” would typically convey in this context.

So fond of is the best choice because it naturally captures a broad, affectionate liking for the activities described.