According to the passage, we know the Maya were good agriculturalists because there

is evidence that

A

they studied planets and stars.

B

they built over 3,000 buildings.

с

they practiced intercropping.

D

they build huge cities.

The answer is B because it shows that they built a lot buildings which would appear as if they were great agriculturalists

Well since you haven't shared the passage it makes this hard. But you can rule out B and D because buildings and huge cities have nothing to do with agriculture. But they did practice intercropping so I would go with C.