下列各式是最简二次根式的是(       )．

    Do you often use a cell phone? Do you take the subway（地铁）to school every day? These items（项目） make our modern life easier. But do you know how we should behave properly while using them? The following suggestions might be helpful.

    For cell phone users

    ◆Keep your voice down when you make a phone call in public. Shouting on the phone may make others feel uncomfortable. And you'd better not use it during an appointment（约会）.

    ◆Stop sending messages or playing games with your cellphone at a dinner or a party. It's a good time to communicate with your family and friends.

    ◆Don't make or answer a call while driving. It is very dangerous for both you and your passengers.

For subway passengers

    ◆You are supposed to wait in line while buying tickets and getting on the subway.

    ◆You're not allowed to eat, drink or smoke on the subway train. The smell and noise may trouble others. It's our duty to keep the train clean and tidy. Besides, smoking is bad for health.

    ◆ You can't take pets on the train. As we all know, animals may spread diseases (疾病),  get the train dirty and make much noise.

    ◆ You'd better not lie across the subway seats even if the train isn't crowded. Offering your seat to someone who needs it is regarded as good manners.

19世纪末，中国一位官员在出使某国后感叹，“推原其立国本末，所以持久而国势益张者，则在议政院有维持国是之义；设市长治民，有顺从民意之情，二者相持，是以君与民交相维系，迭盛迭衰，而立国千余年终以不敝，人才学问相承以起”。该官员称赞的国家是（    ）

梯度转移是指一个国家的经济发展客观上存在梯度差异，高梯度地区通过不断创新并不断向外扩散求得发展，中、低梯度地区通过接受扩散或寻找机会求得发展。下图为“中国区域间产业转移梯度模式”图，读图完成（1）～（3）题。