皮带机运转过程中，头部伸缩装置（），待皮带机停机后才可进行（）．
参考答案：禁止操作；车体部分移动
He writes so _____ that everybody learns _____ him. [ ]
A. carefully; from
B. more careful; to
C. much more carefully; from
D. much more careful; at
多媒体具有多样性、交互性和()特点。
A．可控性
B．保密性
C．通用性
D．集成性
