This seems like a textbook question. If the textbook doesn't contain the answer, it seems your teacher is expecting you do to some research yourself.
Let me only say that I find it a rather old-fashioned question. Who cares about the inner workings of his Pentium chip today? It just works.
Anyway, we never do your homework here: you've got to do it yourself.
please tell me difference b/w ALU and CU