早产儿视网膜病变的治疗原则是（） A.对Ⅲ区的1期或2期病变密切观察病情变化 B

根据对话内容，判断句子正(√)误(×)。

Amy: What can you do at home, Chen Jie?

Chen Jie: I can set the table and do the dishes. What about you, Amy?

Amy: I can make the bed.

Chen Jie: Can you wash the clothes?

Amy: No, I can't, but I'd like to have a try.

( ) 1. Chen Jie can set the table.

( ) 2. Amy can make the bed.

( ) 3. Amy can wash the clothes.

在常量分析时，载气、氢气和空气的纯度在( )以上即可。

A．99.9%

B．99.999%

C．95%

D．90%

牙髓塑化治疗的非适应证是

A．乳牙慢性根尖周炎
B．年轻恒牙牙髓坏死
C．成年人前牙牙髓根尖周病
D．成年人后牙根尖孔破坏疾病
E．以上各项均是

简述什么是颅内压增高？

民用航空器必须具备民航颁发的（）方可放行.

A.生产许可证

B.适航证

C.型号合格证