致畸指数是指母体LD50与胎仔最小致畸作用剂量之比，比值越大，致畸作用越强。
参考答案：对
—Is it an interesting job?
—I don't think so. ________. [ ]
A. It's fun
B. It's very interesting
C. It's kind of boring
下面哪种疾病可造成视力减退和失明（）
A.结膜炎
B.重症沙眼
C.假性近视
D.弱视
E.泪囊炎
