如图虚线框内的装置叫____ ，其中R是热敏电阻，它的阻值随温度的升高而减小，R₀是滑动变阻器．该装置的工作原理是：随室内温度的升高，热敏电阻的阻值减小，控制电路中电流增大，当电流达到一定值时，衔铁被吸合，右侧空调电路接通，空调开始工作．为了节能，现要将空调启动的温度调高，可以适当将滑片P向____ （左或右）移动，或者适当____ （增大或减小）控制电路的电源电压．

据报道，北京市今年开工及建设启动的8条轨道交通线路，总投资约82 000 000 000元．将82 000 000 000 用科学记数法表示为（　　）

下面是使用显微镜对光和观察的步骤，排序正确的选项是（    ）

①将玻片标本放在载物台上，使玻片标本正对通光孔的正中心

②转动转换器，使低倍镜对准通光孔

③双眼从侧面注视物镜，旋转粗准焦螺旋使镜筒下降接近玻片标本

④调节光圈和反光镜，直到看到明亮的圆形视野

⑤一只眼看目镜，旋转粗准焦螺旋使镜筒缓缓上升直到看到物像．

阅读下面短文，根据短文内容，完成下列各题。

    Americans spend their weekends in different ways. But usually they choose the same aim—to rest and to enjoy the time with their family and friends.

    Some Americans hold parties on Saturday nights. They will dance, sing and drink together till midnight. Then they won’t get up until 9, 10 or even 11 o’clock next morning. As soon as they get up, they will go to the nearest corner shop to buy the daily newspaper. They can get news about films, plays, shows and sports in the paper. It will help them decide what to do on Sunday afternoon.

    Before going out on Sunday, they will have a meal, which is called brunch. They will make it at home or go to a restaurant nearby. After brunch some Americans have a picnic with their family or friends. They will take many things with them, such as fresh vegetables, sea food, drinks and table cloths. Usually they drive to a beautiful park, a lake or the seaside.

    Sunday dinner is the most important and the biggest meal of the week and all family members try to show up.