预应力混凝土构件中，下列何项适合采用先张法施工()
A．大型构件
B．工厂预制的中小型构件
C．现浇构件
D．曲线预应力钢筋
参考答案：B
4x2+2y-3xy+7+3y-8x2-2合并同类项的结果有（ ）
A．一项
B．二项
C．三项
D．四项
These days our _____ concern is to provide people with enough information about food safety. [ ]
A. normal
B. constant
C. permanent
D. primary
