—Where is Tom?

— Well, he ______ you ______ here．Otherwise he would come down right now．

A．didn’t know; were

B．hasn’t known; are

C．doesn’t know; are

D．hadn’t known; were

我国《计量法实施细则》规定，凡制造在全国范围内从未生产过的计量器具的新产品，必须经过----。定型鉴定合格后，应当履行----------手续，颁发证书。