Answer:
Step-by-step explanation:
It is the subject of the verb became. Therefore it is a gerund phrase.
I am taking the words in question were Helping the poor ...
It is not an appositive. An appositive phrase is something like
James, the apostle, was a very practical man. James and apostle are the same person.
An infinitive phrase is something like
To know is to understand. Infinitive phrases are characterized by to.
The second best answer is a prepositional phrase, but helping the poor does not describe became and even if it did, it would leave the sentence without a subject.