适合于工程作业船的锚是：（）
A.无杆锚
B.有杆锚
C.大抓力锚
D.特种锚
参考答案：C
The place______ the bridge is supported to be built should be _____ the cross river traffic is the heaviest
A．which; where
B．at which; which
C．at which; where
D．which; in which
数据库系统的核心是______。
A．数据库
B．数据库管理系统
C．数据模型
D．软件工具
