视物变形主要是哪一类疾病的症状（）
A.视神经炎
B.黄斑疾病
C.白内障
D.青光眼
E.屈光不正
参考答案：B
（）不会影响压力过滤罐的水质效果。
A、来水含油高
B、反冲时间长
C、滤料流失
D、滤层结垢
There isn't _____ in this lesson. [ ]
A. something difficult
B. difficult something
C. anything difficult
D. difficult anything
