ACT English question. Explain why this is wrong

ArenasField
Wed, 10 Apr 2013 13:34:57 +0000

“It is difficult to say from which civilization calligraphy directly emerged.”

F)no change

H) From which civilization calligraphy directly emerged is difficult to say."

Why is the answer F, and not H?

They both sound fine to me, and although I would normally use and write choice F, I thought that it was bad to use the word “it” without it being properly defined beforehand.

Can anyone shine some light on this and explain the situation?
When is it okay to start a sentence with it/use it in a sentence?

Thank you so much.