下列运算正确的是[ ]
A.x5+x5=x10
B.x5·x5=x10
C.(x5)5=x10
D.x20÷x2=x10
答案:B
John thinks it won’t be long_________he is ready for his new job.
A.when
B.after
C.before
D.since
安装活塞环时,有文字或记号面朝上,压缩环上下环可互换。