建设工程项目进度计划系统是由多个（）的进度计划组成的，它是项目进度控制的依据。
A．相互独立
B．相互交替
C．相互搭接
D．相互关联
参考答案：D
By the time Jack returned home from England, his son. from college.
A．graduated
B．has graduated
C．had been
D．had graduated
急性毒性观察实验期一般为
A．28天
B．10天
C．14天
D．7天
E．21天
eturned home from England, his son. from college.