单选题 If the computer ______ the computations, a signal will be given at once.
A. will finish B. is finishing
C. is going to finish D. has finished

【正确答案】 D
【答案解析】[解析] 现在完成时用在时间或条件状语从句中，表示将来某个动作发生之前已完成的动作。