Technology is developing so rapidly that _____ for only a year, my cellphone is out-of-date. [ ]
A. using
B. having been used
C. having used
D. is using
答案:B
Technology is developing so rapidly that _____ for only a year, my cellphone is out-of-date. [ ]
A. using
B. having been used
C. having used
D. is using
答案:B