Who was ______ spoke first at the meeting?
A.that it
B.it that
C.it what
D.what it
答案:B
试述羊水过少的原因。
髓鞘的主要蛋白成分是()
A.脑苷脂,磷脂
B.磷脂,胆固醇
C.胆固醇,蛋白脂蛋白
D.蛋白脂蛋白,髓鞘碱性蛋白
E.髓鞘碱性蛋白,脑苷脂