21．——May I speak to_______ proffessor Black , please ?
——Sorry , but he is busy conducting ________ experiment in the lab right now.
A. the ; an B. a; the C. / ; an D. the ; the
22. ——May I take your order now ?
——_________。
——OK , I’ll come back in a few minutes
A. No, we need more time B. What can I do for you ?
C. Yes, here it is, thank you. D. Sure , we’d love to
