构成机械密封的基本元件有：端面密封副、（）、辅助密封、传动件、（）和紧固件。
参考答案：弹性元件；防转件
看图写答句。
1.-What is Christmas?
-Christmas is a s____ h____.
2.-What is Lynn going to do?
-She's g____ t____ o____ her gift.
3.-What is Li Ming doing ?
-He's g____ a g____ to them.
4.-What are they putting on the Christmas tree ?
-They're putting on the l____.
5.-What's this?
-It’s a g ____.M____ Christmas!
任务结构
