小华用20N的力把重为25N的物体沿着长为20cm、高为10cm的斜面，从斜面底端拉到顶端。则斜面的机械效率为________。
62.5％
It is reported that a new racing car made from vegetables and powered by chocolate ______in
May, 2009.[ ]
A. will be launching
B. was launched
C. has been launched
D. has launched
病毒性脑炎最常见的病原体属于（）
A.肠道病毒
B.虫媒病毒
C.疱疹病毒
D.腮腺炎病毒
E.副流感病毒
