We don't know his telephone number; if we ____, we _____   him now. [ ]

A. know; must telephone

B. knew; would telephone

C. have known; have telephoned

D. knew; have telephoned

免疫缺陷病

A．属于生理性免疫防御
B．属于病理性免疫防御
C．属于生理性免疫自稳
D．属于病理性免疫自稳
E．属于免疫监视