Like other animals, we are ________ until we know it is safe to relax.
A.on purpose B.on fire C.on guard D.on duty
When ________ to someone，I usually say，“Pleased to meet you.”
A.introduce B.introduced C.introducing D.am introduced
—Tommy is planning to buy a car.
— I know. By next month, he ____ enough for a used one.
A.saves B.saved C.will save D.will have saved
He wins the Nobel Prize for his outstanding _________to physics.
A.contribution B.conclusion C.addition D.explanation
All the neighbors admire this family _____ the parents are treating their child like a friend.
A.why B.where
C.which D.that
A good advertisement often uses words ________people attach positive meanings.
A.that B.which C.with which D.to which
