只有多于一条多肽链的蛋白质分子才有四级结构。单独的亚基不具有生理活性，只有亚基相互结合构成的四级结构才有生理活性。
A、正确
B、错误

Some people claim that technology creates more problems...

未知题型Some people claim that technology creates more problems than it solves, and may threaten or damage the quality of lifE.What do you think of this statement? Write an essay of about 400 words.
In the first part of your essay you should state clearly your main argument, and in the second part you should support your argument with appropriate details. In the last part you should bring what you have written to a natural conclusion or make a summary.
You should supply an appropriate title for your essay.
Marks will be awarded for content, organization, grammar and appropriateness. Failure to follow the above instructions may result in a loss of marks.

For centuries, Chinese people have been encouraged to f...

未知题型For centuries, Chinese people have been encouraged to fight back against crime and help out with emergencies in a selfless manner. However, should our youth sacrifice their lives in an emergency or is there a smarter way to deal with a crisis? Write a composition of about 400 words to state your view.
In the first part of your essay you should state clearly your main argument, and in the second part you should support your argument with appropriate details. In the last part you should bring what you have written to a natural conclusion or make a summary.
You should supply an appropriate title for your essay.
Marks will be awarded for content, organization, grammar and appropriateness. Failure to follow the above instructions may result in a loss of marks.

中心静脉营养的优点包括()A、适宜于营养治疗不超过2周的病人B、输入液体很快被稀释，对血管刺激小C、可最大限度...

多项选择题中心静脉营养的优点包括()