清代北方园林建设的主流是（） A.皇家园林 B.山水园林 C.私家园林 D.公共园林

去甲肾上腺素的特点有

A．含有儿茶酚结构，易被氧化变色

B．含有儿茶酚结构，易被儿茶酚氧甲基转移酶代谢失活

C．含有伯氨基团，可被单胺氧化酶氧化代谢失活

D．含有一个手性碳原子，用其左旋异构体

E．在有些金属离子催化下，氧化速度加快

阅读理解。

     You've probably heard countless times how exercise is "good for you", but do you know that it can

actually help you feel good, too? Getting the right amount of exercise can speed up your energy levels

and even help you to feel better emotionally.

     However, like all good things, it's possible to overdo on exercise. Although exercising is a great way

to maintain a healthy weight, exercising too much to lose weight isn't healthy. The body needs enough

calories to function properly. Remember that you're still growing and will continue to do so throughout

your teen years. You'll need the energy to fuel the growth.

     Exercising too much in an effort to burn calories and lose weight can be a sign of an eating disorder.

If you have any doubts about how much you should be exercising, talk with a school nurse or family

doctor. And if you ever get the feeling that your exercise is in charge of you rather than the other way

around, talk with your doctor, a parent, or another adult you trust.

     Considering the benefits to the heart, muscles, and mind, it's easy to see why exercise is wise. If you

exercise now, keep it up as you become an adult (this is often the biggest exercise challenge for people

as they get busy with college and careers). One of the great things about exercise is that it's never too

late to start. And don't forget that even small things can count as exercise when you're starting out-like

taking a short bike ride or sweeping fallen leaves. Even walking your dog counts as part of your 60 minutes

a day of exercise (and your vet will tell you that animals need workouts just like humans do, so if your

family dog is fat, he'll benefit from your dedication, too).

1. Why should teens not exercise too much?

A. Because it causes their body to work disorderly.

B. Because it gets them to have an unhealthy weight.

C. Because it will make them become too thin.

D. Because it burns the energy they need to grow up.

2. The underlined part in Para.3 means that _____.

A. you are charged for your exercise

B. you manage how much exercise you need

C. you are greatly addicted to exercising

D. you do some exercise free of charge

3. What is the biggest challenge for people who want to exercise?

A. To find enough time to exercise.

B. To continue to exercise the whole life.

C. To own suitable equipment for exercising.

D. To find a person to exercise together.

4. The subject discussed in Paragraphs 2-3 is that _____.

A. it is not good for you to exercise too much

B. it is helpful to lose weight by exercise

C. it is a good thing to exercise every day

D. it is good for your pet to exercise every day

电流的磁效应现象说明（）。

关于抵押物的保全，以下说法错误的是( )。

A．在抵押期问，银行若发现抵押人对抵押物使用不当或保管不善，足以使抵押物价值减少时，有权要求抵押人停止其行为

B．若抵押人对抵押物价值减少无过错的，银行可要求增加担保

C．抵押权与其担保的债权同时存在，债权消失的，抵押权也消失

D．若抵押物价值减少时，银行有权要求抵押人恢复抵押物的价值，或者提供与减少的价值相等的担保

疲劳强度是指金属材料在无数次交变应力作用下，引起破坏断裂的最大应力。（）