Answer:
The sentence that contains a present participle of the verb to collect is sentence B.
Step-by-step explanation:
A participle typically expresses present action with respect to the time expressed by the finite verb in its clause and that is formed by adding the suffix -ing. The present participle is used in the formation of the progressive or continuous tenses. In the sentence above, you can see that the event is taking place now if you add now (see A).
a) He is collecting rare coins now