Answer:
The correct gerunds to complete the sentences are:
1. Swimming
2. Losing
3. buying
Step-by-step explanation:
A gerund is a variation of a verb that can be used as conjugation in the continuous tenses or as a noun at the beginning of a sentence, trying to make sense with this sentences they would go like this:
Daphne loves swimming.
Losing one's keys is very annoying.
I regret buying those expensive jeans.
All of these sentences use the gerund as a noun.