Answer:
Two sentences use "eating" as a participle:
B. My eating habits are a lot healthier than they used to be.
D. This problem has been eating away at me, and I can't sleep.
Explanation:
The gerund and the present participle are identical to the eye. They both are formed by adding -ing to a verb root. Thus, "eating" can be a gerund or a participle, according to the context.
The difference between them is quite simple. The gerund acts like a noun, having the same functions a noun would have in a sentence: subject, object of a verb or of a preposition, and subject complement. The present participle, on the other hand, will either act as an adjective, modifying a noun or a pronoun, or be a part of a continuous tense.
That is precisely what we have in options B and D. In option B, "eating" is an adjective modifying the noun "habits". In letter D, "eating" is a part of the Present Perfect Continuous tense. Therefore, in options B and D, "eating" is a participle:
B. My eating habits are a lot healthier than they used to be.
D. This problem has been eating away at me, and I can't sleep.
