新生儿生理性黄疸产生的最主要原因是()
A.胆红素产生过多
B.肝酶系统发育不完善
C.肝肠循环增加
D.胆红素产生过多及肝酶系统发育不完善
E.以上都不是
参考答案:D
—Is Bill in?
—No, he _______ to the railway station. [ ]
A. has gone
B. had gone
C. has been
D. had been
潮汐