—It is said that Jack is very rich and is always changing his private cars. What is he?—________, I am not sure.
You ______ be driven out of the school if you dare to cheat in the exam.
On hearing a great noise, Mike looked forward through the window _____ what happened outside the room.
We hadn't met for 20 years, but I recognized her_____ I saw her.
________evidence that language acquiring ability must be stimulated.
The professor could hardly find sufficient grounds _____his arguments in favor of the new theory.