The answer is A, i'm also on study island on this test. It has a star next to it. So yep we're right!
Answer - A. an agricultural system
Explanation - Anything that has two or more parts working together is a type of system. Some systems, such as toothbrushes, are very simple because they only have a few parts. Other systems, such as farms, can be very complex because they have hundreds of different parts. The components of a system play different roles in the system.
Plus study island:D