Here was the question:

What's wrong with this sentence? "Citrines whose colors have been produced by artificial means tend to have much more of an orange or reddish caste than those found in nature."

Nothing	9 (13%)
Punctuation	22 (33%)
Spelling	19 (29%)
Grammar	15 (23%)

Congratulations to 29% of you. The spelling of "caste" should have been "cast."