Final answer:
The best meaning of "incredulous" in the given sentence is disbelieving.
Step-by-step explanation:
The best meaning of "incredulous" in the given sentence is disbelieving. When someone is incredulous, they are unwilling or unable to believe something. In this context, the speaker is describing how they had to make an effort to control their laughter because they found something so unbelievable or absurd.
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