梯形图中V行中的螺旋样竖线表示（）。 A.心房内差异性传导 B.心室融合波 C.交界

Are you carrying too much on your back at school? You’re not alone. Back experts in the United States are worried that young students are having back and neck problems as a result of carrying too much in their backpacks (schoolbags)

“It hurts my back when I run,”said Oberlin Reyes, a student in Virginia. “It’s hard to go up the stairs with my backpack,because it’s too heavy,”

Oberlin was among students whose backpacks were weighed for a week in a recent study.

They had regular backpacks with two straps(带子)to carry them, but a number of students with heavy loads had switched to rolling backpacks (which have wheels and can roll on the ground).

Shirley Park, whose backpack weighed 10 kilograms,said she changed to a rolling backpack because she was starting to have back  pain.

How much is too much?Experts say students should carry no more than 10 to 15 percent of their own body weight.

A few students had one suggestion to lighten the load:less homework.

P.S.( 附)Doctor’s suggestion:

1 Lighten the load. Clean out binders(活页材料)and take home only the books you need that night.

2 Wide straps are better. They send out the weight over your shoulders more evenly(均匀)。 And be sure to wear both straps rather than hanging the pack over one shoulder.

3. Pack smart. The heavier things should be packed closed to the back.

4.Bend both knees when you pich up the pack ,and don’t just bend over  at the waist.(腰)

小题1:“_________”is the main idea of the text.

A The problem of backpacks is worth studying.

B The problem made by heavy backpacks

C What is the best backpack for a student.

D      How to make students’backpacks light.

小题2:According to Oberlin Reyes and Shirley Park, we know________.

A students have to do too much homework

B students have to carry several backpacks

C backpacks without wheels are bad for students

D too much homework leaves students no free time

小题3:The expression “switched to” in the text perhaps means________.

A started to use  B turned to  C caught up   D used for

小题4:According to the passage ,it’s better for a student of 40 kilograms to carry a backpack of _____at most by the words of experts.

A 10kg    B 8kg  C 6kg    D 7kg

小题5: If students follow the doctor’s suggestions they ________.

A may lighten their backpacks

B can learn how to help themselves

C may feel their backpacks are lighter

D will know how to wear backpacks

近年来，由于石油等能源消耗量的急剧增加，给环境造成巨大的压力。核能作为一种新型能源，被许多国家所利用。核能将会成为满足人类需要的能源。但核能在给人类带来巨大利益的同时，也伴随着一定的安全风险。因此，开发利用核能我们必须以确保安全为前提。

运用哲学知识简要回答：

（1）能源消耗和环境压力是一种什么联系？

____________________________________________________________________________________________________________________

（2）我们如何正确看待“核能的发展”？（选择唯物辩证法或认识论的一个观点 回答）

____________________________________________________________________________________________________________________

军事法的本质

（）是指考评者仅凭下属最初的绩效信息，对考评期内的全部表现做出总评价。

A．优先效应

B．首因效应

C．后继效应

D．近期效应

再热器汽温调节的常用的方法有：摆动式燃烧器、烟气再循环、分隔烟道挡板调节、喷水减温器（一般作为事故处理时用）。