目前我国致盲的首位原因是（）
A.沙眼
B.青光眼
C.糖尿病性视网膜病变
D.白内障
E.老年性黄斑变性
参考答案：D
用所给词的适当形式填空。
1. At school we are all (friend) to each other.
2. I'm going to have my (twelve) birthday party next Monday.
3. It’s (wind) today, we can't go shopping.
4. Tom is (real) good, isn’t he?
5. There are three girls waiting (cross)a busy street.
水不溶性半合成高分子囊材为（）。
A．壳聚糖
B．EC
C．β-CD
D．PLA
E．枸橼酸
