通过发票发售系统发售发票必须遵循的原则（）。
A.先卖票后报税
B.先报税后买票
C.限量限额、验旧购新
D.先认证后买票
参考答案：B, C
逆行肾盂造影选用 （）
A.亚甲蓝
B.胆影葡胺
C.碘化钠
D.碘油
E.碘番酸
An 8 percent coupon bond with a par value of $100 matures in 6 years and is selling at $95.51 with a yield of 9 percent. One year ago this bond sold at a price of $90.26 with a yield of 10 percent. The bond pays annual interest. The change in price attributable to the change in maturity is closest to:（）
A. $1.03.
B. $4.22.
C. $5.25.
