判断胎儿肺成熟度（）
A.L／S比值
B.NST
C.羊水穿刺
D. * * 涂片细胞学检查
E.OCT
参考答案：A
He stepped into the dark cave, _______ high above his head.
A．holding a burning stick
B．held a burnt stick
C．holding a burnt stick
D．held a burning stick
双绞线的电气特性“NEXT”表示______。
A．衰减 B．衰减串扰比 C．近端串扰 D．远端串扰
