Hi there,

I would like to know how to proceed in order to resolve this SC :

Before scientists learned how to make a synthetic growth hormone, removing it painstakingly in small amounts from the pituitary glands of human cadavers.

(A) scientists learned how to make a synthetic growth hormone, removing it painstakingly
(B) learning how to synthesize the growth hormone, it had to be painstakingly removed by scientists
(C) scientists had learned about making a synthetic growth hormone, they had to remove it painstakingly
(D) learning how to make a synthetic growth hormone, scientists had to remove it painstakingly
(E) scientists learned how to synthesize the growth hormone, it had to be painstakingly removed