We asked if they had experienced any camping difficulties.

a.

participle

b.

gerund

c.

infinitive

If the idea is to classify the word "camping", it can be said that the correct option is A participle

This is because it comes from the verb "camp" and it functions as an adjective because it is modifying "difficulties"

In the case of a gerund. it would function as a noun and the infinitive form does not have the ING inflection.

It would be A; participle.