米托葸醌为（）。

A．抗代谢药物

B．抗肿瘤抗生素

C．抗雌激素类药物，治疗乳腺癌

D．抗肿瘤植物药有效成分

E．抗肿瘤金属配合物

–Why, I couldn’t get you on the phone this morning.

--We _____ tennis in the yard when you called.

A．must be playing

B．could be playing

C．must have played

D．must have been playing