无内胎轮胎的缺点是()和自粘层容易漏气。
参考答案:密封层
甲肝病毒是( )
A.杯状病毒B.嗜肝DNA病毒C.缺陷病毒D.黄病毒E.微小RNA病毒
The young men walked _____ the forest and came to a big river at last. [ ]
A. on
B. over
C. through
D. across