The sentences that have
gerund are first, second, fifth and sixth sentence. The gerund has the same
form as a present participle, but the gerund always has the same function as a
noun with different uses.
In the first sentence (Slithering
snakes are common on the trail.) gerund is “slithering” and is used in compound
noun.
In the second sentence
(With all the walking, you must be tired.) the gerund “walking” is used as a
subject.
In the fifth sentence (Watching
television is my favorite way to relax.) the gerund “watching” is used as
subject.
In the fifth sentence (Yawning
can be contagious.) the gerund “yawning” is used as the subject.
2,5, and 6