术前常规禁食的时间是
A. 禁食4小时,禁水2小时
B. 禁食6小时,禁水2小时
C. 禁食8小时,禁水3小时
D. 禁食10小时,禁水3小时
E. 禁食12小时,禁水4小时
如果( )等于或者大于社会折现率,表现建设项目资源配置的经济效率达到了可以被接受的水平。
A. 费用效益率
B. 经济净现值
C. 经济内部效益率
D. 效益费用比
To______ the students' life on campus, the university has established many recreational facilities.
A. verify
B. convey
C. enrich
D. enhance
The mother said she would______ her son washing the dishes if he could finish his assignment before supper.
A. let down
B. let alone
C. let off
D. let out