Fill in the gap with the most appropriate option from the list following the gap.
The old man couldn't help _____ at his grandson's babbling?
Answer Details
The most appropriate option to fill in the gap is "laughing."
The sentence is in the past tense, and the phrase "couldn't help" suggests that the old man was unable to control his laughter. Therefore, the correct form of the verb to use here is the -ing form, which indicates an ongoing or continuous action in the past.
The other options do not fit because "to laugh" suggests an intention or purpose, rather than an inability to control laughter. "That he laughed" is a clause and does not fit grammatically in this sentence. "In laughing" is a prepositional phrase and does not make sense in the context of the sentence.