Nomads is the right answer.
Anyone who moves from one place to another rather residing in one place is called the nomads. There can be many reasons for the migration of the nomads such as herders change places because of the weather( that is not suitable for their animals). whereas, other nomads including that of the traders and merchants, travels move for exchanging of their goods.
I think the answer is D, I might be wrong though but hope I helped! Sorry if I didn't!
Teaching them how to speak English
