下列哪一种试验反映胎儿肺发育是否成熟()
A.羊水泡沫试验
B.肌酐测定
C.葡萄糖测定
D.胆红素测定
E.淀粉酶测定
参考答案:A
Here is a train that has just come in, with crowds of people _____ off it.[ ]
A. being gotten
B. to get
C. getting
D. gotten
简述汉武帝中央集权的措施。