请教新prep1-68

For the best extraction of the flavor of saffron threads, it should be soaked in liquid after being pounded with a mortar and pestle.

(A) For the best extraction of the flavor of saffron threads, it should be soaked in liquid after being pounded

(B) To best extract their flavor, saffron threads should be soaked in liquid after pounding

(C) The best way to extract the flavor from saffron threads is soaking them in liquid after being pounded

(D) The best way to extract the flavor from saffron threads is to soak them in liquid after pounding them

(E) The flavor of saffron threads can best be extracted by soaking it in liquid after pounding it

 答案：D

不理解为什么是is to soak，开始看见be to do就直接排除了 后来发现is是与way搭配的 但是to soak仍然不明白为什么这么用