Each of those machines in the past can only perform ______.

A．She wants the man to listen to the instructions and observe.
B．She wants the man lo watch while she performs the operations.
C．She wants the man lo ask questions so that she can help him.
D．She wants the man to try to do it while she gives him instructions.

A．The man is learning how to use a computer.
B．The woman is showing the man how to put page numbers on a document.
C．The man is printing a document.
D．The man is using his computer to do mathematical functions.