I picked this up from the about.com website. Where else!
Choose the correct grammar structure to complete the sentence. The question has only one correct answer. You will likely solve it in a minute. Wanna try your luck at it?
Q: _____________________________________, I would have returned it immediately.
a) If I knew that you wanted to read it
b) I had known that you wanted to read it
c) Had I known that you wanted to read it
Do you happen to have any TOEFL-type quiz or quizzes that you would like to post? Why not do it here?