该产妇最可能的诊断为
A.过期妊娠B.胎盘功能不良C.胎儿宫内窘迫D.宫缩过强E.脐带脱垂
参考答案:C
—When is Jack going to finish writing that program?
—I don't know ______ day in and day out.[ ]
A. He has been working
B. He has worked
C. He had been working
D. He was working
概括说明σ因子对启动子调节的辅助功能。