宫底在脐上3横指（）
A．孕16周
B．孕20周
C．孕28周
D．孕36周
E．孕40周
参考答案：C
Tom is good a student he is often praised by the teacher.
A．such; as
B．so; as
C．such; that
D．so; that
重量分析对沉淀的要求是什么？
