In the office an electrical engineer is looking through the instructions to know ________ the heat system works before the repair work.
A．whether B．why
C．how D．that
Energy, passion and a burning desire are, you see, ________ true learning takes.
A．that B．what
C．how D．which
________ is the most important for him is not his job, but his family.
A．It B．As
C．What D．That
________ she was invited to the ball made her very happy.
A．Whether B．That
C．Because D．What
Mary is a humorous and warmhearted woman and that is ________ she is a most popular person in her community.
A．whether B．because
C．how D．why
The organizers promise ________ wins the first prize a chance to go abroad.
A．who B．whom
C．whoever D．whomever
