图是广州、武汉、北京和哈尔滨四地气候统计图，其中能反映北京气候特点的是（  ）

 已知a、b、c三种物质的溶解度曲线如图1，根据题意回答下列问题．

（1）下列说法中，正确的是____ ．

A．a与b相比，a的溶解度大于b的溶解度

B．在t₁℃时，a与b的溶解度相等

C．t₂℃时，将30g a物质溶于50g溶剂中，可得到80g溶液

D．从t₂℃降温至t₁℃时，c有晶体析出

（2）如图2所示，将盛有c物质饱和溶液的试管置于盛有适量水的烧杯中，需向烧杯内加入下列哪种物质，才能使试管内的饱和溶液变为不饱和溶液____ 

A．浓H₂SO₄   B．氢氧化钠    C．蔗糖    D．食盐    E．硝酸铵．

     If you have dinner with people in the west, I think you must pay more attention to the table manners. Here are some good table manners for you.
     When you eat something, try not to make a noise or burp (打嗝) at the table. Because people think that is not polite. People will say “Excuse me” when they want to burp.
      Talking with food in the mouth is very rude. So you must eat the food quietly and slowly. If you eat too fast, people think you are rude too. Do not talk with others when you have food in your mouth.
      It is good to eat all the food on your plate. This means you like the food very much. Remember to say the food is nice. And this can make the host very happy. When you finish eating, you can place your knife and fork together.