找出与所给单词划线部分发音相同的单词，写在横线上。

pass         smile         slow         car

slipper      vase          smell        arm

smoke      hard          glass        slip

1. class:                                            

2. small:                                            

3. sleep:                                             

4. park:                                             

什么叫HC轧机？HC轧机的优点是什么？