【判断题】发动机活塞环中油环的主要作用是密封作用。
【单选题】When Li Ming introduced Deng Ling to Mary, he said________.
A.
I’d like you to meet my friend Deng Ling.
B.
Please allow me to introduce my friend Deng Ling to you.
C.
Come to meet Deng Ling.
【判断题】活塞环中气环的主要作用是封气,油环的主要作用是刮油。 ( )