多普勒雷达速度图中，零值等风速线呈反S形，表示风向从地面向高空（）旋转变化，有（）平流。

A.顺时针；暖

B.逆时针；暖

C.顺时针；冷

D.逆时针；冷

An analyst is doing research about the change of bond value to the passage of time and gathered the following information about an option-free bond. The bond has 6 percent coupon and an annual discount rate of 5 percent, pays interest semiannually, matures in five years, and is valued at $1043.76. One year later, the annual discount rate for that bond is 4.5 percent. At this time, the change in value for this bond that is attributable only to change of interest rate is closest to:（）

A. -$18.50

B. $7.91

C. $18.50