He asked them to come to his office one . A. at a timeB. at all timeC. at timesD. at one t

网友回答

(答案→)A. at a time
B. at all time
C. at times
D. at one time
解析：考查词组：A. at a time一次B. at all time一直C. at times有时D. at one time曾经，句意：他叫他们一次一个去他的办公室。选A。