请根据下列叙述，用化学式或名称填空： （1）它在海水中蕴藏丰富，是人的正常生理活

曲线y=3x²+1，x=0，y=0与x=2所围成的曲边梯形的面积为（）．

How would you like to live in a land where the sun shines day and night? There are place in the polar regions where, for North, the sun never sets! This is known as the land of the Midnight Sun. This period of sunlight can last up to six months.

This happens because the Earth tilts(倾斜). When the North Pole is tilted towards the sun, it has constant (不断) daylight. As the same time, the South Pole is tilted away from the sun. It is in darkness.

Six months later, the South Pole tilts to the sun and has constant daylight. Then the North Pole is tilts away. It has darkness.

小题1: Where can you see the Midnight Sun?

小题2:How long can the period of sunlight last?

小题3:Why can we see the Midnight Sun?

小题4:When there is Midnight Sun in the North Pole?

小题5:What happens in the South Pole?

以下是有关激光打印机的叙述： Ⅰ． 由于激光能聚集成很细的光电，所以激光打印机的分辨率较高 Ⅱ． 激光打印机中有一个“页面存储器”，用于存储整个页面的点阵图像 Ⅲ． 激光打印机是一种页式打印机，其打印速度的单位是PPM Ⅳ．目前多数激光打印机通过USB接口与PC机连接 上述叙述中,正确的是

A．仅Ⅰ和Ⅱ

B．仅Ⅱ、Ⅲ和Ⅳ

C．仅Ⅰ、Ⅱ和Ⅲ

D．全部

设备清洗中除应遵循常规的技术要求外，还应注意加工表面的锈蚀处，用油无法擦去时，可用棉布蘸( )擦去。

A．酒精

B．香蕉水

C．丙酮

D．醋酸