Sandy sits between ______ and ______ .

I found ________ difficult to work out the problem without a computer.

Whenever I go to Beijing, ____ is quite frequent, I will go to visit the Great Wall.

Is Jack on duty today? —It ______ be him. It is his turn tomorrow.

Shirley won the first prize in the English speech contest. —Woo! ________ she has made since the beginning of this term!