6岁的孩子，腕部骨化中心出现的数目为（）

A.4个

B.5个

C.6个

D.7个

E.8个

Discretionary fiscal policy can be defined as:（）

A. a situation in which total government spending exceeds total government revenue during a specific time period, usually one year. 

B. a change in laws or appropriation levels that alters government revenues and/or expenditures. 

C. a situation in which total government spending is less than total government revenue during a time period, usually one year.