巴豆去油制霜的操作过程是（）

A.取药去壳取仁→碾捣→蒸热→压榨→吸油纸包裹→反复换纸吸油至松散粉末

B.碾捣→取药去壳取仁→蒸热→压榨→吸油纸包裹→反复换纸吸油至松散粉末

C.碾捣→取药去壳取仁→吸油纸包裹→蒸热→压榨→反复换纸吸油至松散粉末

D.碾捣→取药去壳取仁→蒸热→吸油纸包裹→压榨→反复换纸吸油至松散粉末

E.取药去壳取仁→碾捣→吸油纸包裹→蒸热→压榨→反复换纸吸油至松散粉末

The one-year spot rate is 6 percent and the one-year forward rates starting in one, two and three years respectively are 6.5 percent, 6.8 percent and 7 percent. What is the four-year spot rate（）

A. 6.51%.

B. 6.58%.

C. 6.57%.