上腹部出现顽固性呃逆，首先应想到的原因是（）。 A.术后肠粘连 B.粘连引起胃扭转

实验室采用传统的试验方法对肠杆菌科细菌进行鉴定，请论述其总体鉴定方法和思路。

Are you carrying too much on your back at school? I’m sure lots of children of your age will say “Yes”. Not only the students in China have this problem, but children in the United States also have heavy school bags.

Doctors are starting to worry about young students’ back and neck because their school bags are too heavy for them.

“It’s hard for me to go upstairs with my heavy bag,” said Rick Hammond, an ll-year-old student in the USA.

Rick is among students who have school bags with two straps(带子),and many other students choose rolling(有滚轮的) bags.

But even with rolling bags ,getting upstairs is still a problem for children .Doctors say students should carry no more than 10% to 15% of their own body weight (重量)。

Scott Bautch, a back doctor, said children under Grade 4 should carry no more than 10% of their weight and older children shouldn’t stay with over 15% , because their bodies are still growing.

Teachers and parents should do some things to help children. And the best answer is to have less homework!

小题1:From the passage we cam know that        .

A．only children in China carry too heavy school bags.

B．children in other countries don’t carry too heavy bags.

C．both children in China and the USA carry too heavy school bags.

D．only children in the USA carry too heavy school bags.小题2:Children feel it hard for them to go upstairs because          .

A．they are too young.

B．their school bags are too heavy.

C．they are too heavy.

D．their parents don’t always go upstairs with them.小题3:If a child carries a heavy school bag,        .

A．his back and neck may be hurt.

B．his head and arms may be hurt .

C．his hands may be hurt .

D．his feet may be hurt .小题4:According to the doctor, Scott Bautch, if a child in Grade 5 weighs about 30 kilos, the school bag he carries should not be over          .

A．5 kilos

B．3 kilos

C．5.5 kilos

D．4.5 kilos小题5:Some students think the best answer to this problem is that          .

A．they should have a little homework to do after they get home

B．their teachers had getter not ask them to do any homework

C．they should only take home the books they will read that night.

D．They should use thin books instead of thick ones.

制约我国西北经济发展的主要自然因素是（   ）

A．地形起伏大

B．水源缺乏

C．土壤肥力低

D．温差大

维生素A缺乏症是（）

A．干眼病

B．坏血病

C．癞皮病

D．脚气病

E．佝偻病

性价比导向类型的顾客特点是：（）

A.喜欢直呼其名

B.了解其喜好

C.关注优惠活动

D.确保其了解各种预约方式