Hamlet is slightly afraid of his father's ghost because he does not know if he comes from Heaven or from Hell. The ghost could be evil in intent, trying to steer Hamlet down a path of murder, or he could be the true spirit of his father, trying to prompt him towards revenge.
The subject the explosion of clown crews and the predicate/verb allow are not in agreement because the subject is in the singular form, and the predicate in the plural. This is the correct way to rewrite the sentence:
The explosion of clown crews allows <span>unique styles of dance to evolve, such as krumping. OR
The explosions </span><span>of clown crews allow unique styles of dance to evolve, such as krumping.</span>
She has to occupy her. That's what she has to do.