社会在实施某一药物治疗方案过程中所投入的下列资源属于间接成本的是
A.医生的时间
B.医生的工资
C.劳动力降低或丧失带来的经济损失
D.病人的差旅费
E.因病引起的疼痛
参考答案:C
等差数列{an}中,已知a4=4,则前7项的和为( )
A.28
B.56
C.14
D.不能确定
Kevin kicked the ball so hard that up _____, higher and higher, until it was a small dot in the sky.[ ]
A. it flew
B. flew it
C. did it fly
D. fly did it