The emergent-norm theory of crowd behavior says that _______ 。

A、 there is great social pressure on individuals to behave like others in a crowd, even when they may not agree with the crowd behavior.
B、 although there are different kinds of crowds, all crowds share some characteristics.
C、 because we are faceless and nameless in a crowd, we can show our primitive side.
D、 in crowds, people often behave in a way that is different from their normal behavior.