输送带在托辊间的下垂度不超过托辊间距的（），空段托辊间距，一般为承载间距的（）倍。
参考答案：2.5％、两倍
The manager says he needs an assistant to ________ to deal with the problems that may occur in his
absence.[ ]
A. depend in
B. count on
C. count with
D. turn up
气体型钻井流体主要适用于钻高压油气层。
