I DID NOT UNDERSTAND WHAT THE LECTURER WAS SAYING BECAUSE I HAD NOT...

1. I did not understand what the lecturer was saying because I had not read his book.A. What the lecturer wrote and said was too difficult for me to understand.B. The lecturer's book which I had not read was difficult to understand.C. I found it very difficult to understand what the lecturer said in his book.D. I would have understood what the lecturer was saying if I had read his book.