Have you ever seen the film Titanic? “Titanic” was one of the largest and finest ships in 1912. It hit an iceberg(冰山)on its first sailing from England to America and sank very soon, leaving a love story to the people. Do you know what an iceberg is?

The earth is round, like a ball. The top of the earth is the north. The bottom of the earth is the south. At the top and the bottom of the earth, there is a lot of ice. It is very cold there. Sometimes there is no sunshine for many months. There is ice everywhere all the time. Large pieces of ice fall into the sea. They don’t go to the bottom of the sea. They float(漂浮)near the top of the water. We call these large pieces of ice “iceberg”. Some icebergs are bigger than a tall building. Icebergs are dangerous for ships. Sometimes a ship hits an iceberg.

Then the ship sinks.

You can make a small iceberg. Put a piece of ice in a glass of water. Look ar it. The ice does not sink.

小题1:Titanic is the name of a film and it’s also the name of a _______.

小题2:Titanic sank ________ it hit an iceberg.

小题3:The __________ is very cold in North Pole(北极)and in South Pole.

小题4:At times we can’t see the ___ in North Pole and in South Pole for a long time.

小题5: Icebergs are made of large _________.

根据砂轮机的安全技术要求，下列选项中砂轮机的使用不正确的有( )。

A．禁止侧面磨削

B．不准正面操作

C．不准共同操作

D．禁止正面磨削