一头六吨重的大象呼吸一次大约是（）。
A.10秒
B.5秒
C.1秒
D.0.5秒
参考答案：A
By the time Jack returned home from England, his son. from college.
A．graduated
B．has graduated
C．had been
D．had graduated
应付账款的完整性应怎样审计？
eturned home from England, his son. from college.