Answer:
Hello. You did not present the answer options, but we can infer that the topic sentence that should be added is the one that shows that the volunteers of some activity have a great opportunity to make new friends.
Step-by-step explanation:
The text presented above shows how volunteering is an enriching experience, because it allows individuals to expand their thoughts through interaction with people of different thoughts. Volunteering also allows individuals to meet people with similar thoughts and preferences, which can be very beneficial. In summary, we can say that volunteering allows individuals to make new friends. This statement will contribute greatly to the text if it is presented as a topical sentence, which is a sentence that presents the main subject discussed.