无内胎轮胎的缺点是()和自粘层容易漏气。
参考答案:密封层
The PLA soldiers came to the ruins of Yushu and after ______ seemed to be a long time, they helped some victims out.
A.which
B.that
C.what
D.when
二氧化碳系统动力瓶充装压力一般为()MPa。
A.5~6
B.8~10
C.15~18
D.25~30