I did not read his book. I did not understand what the lecturer was saying.

A. What the lecturer wrote and said was too difficult for me to understand.

I did not read his book. I did not understand what the lecturer was saying.

A. What the lecturer wrote and said was too difficult for me to understand.

B. I found it very difficult to understand what the lecturer said in his book.

C. I would have understood what the lecturer was saying if I had read his book.

D. The lecturer’s book which I had not read was difficult to understand