In recent years presidents have come to rely most heavily on the advice of

In recent years, presidents have come to rely most heavily on the advice of the white house staff Sometimes, the person the became the president of the united states does not have a background in Government (they might came from business or entertainment background) in that case, it will be very likely that he will rely on the white house staff to learn the way Government operate

B

Explanation:

Archaeological Sources - any material remains of past human life or activities which are of archaeological interest

The most information for the Olmecs came from their statues and archaeological finds from the era. Their statues that were founded were the most informatory source and is the majority of the knowledge we have today.

I hope this helped :)