各类放线菌能否产生菌丝体，取决于种的特征、（）和环境因子。
参考答案：营养条件
孕期血容量增加需铁
A．子宫托B．Manchester手术C．阴式全子宫切除术D．开腹全子宫切除术E． * * 纵隔成形术
I have been living in the United States for twenty years, but seldom _____ so lonely as
now. [ ]
A. have I felt
B. I had felt
C. I have felt
D. had I felt
