This book_______ 10 units , _______ two revision units.

nservation area is very important for preservingmany animals and plants, which would ______ run the risk of becoming extinct.

When the students arrived there out of ______, the train _______ for about five minutes.

Many experts agree that once these treasures are _______ to the air, great harm will be done to them. So they think it better not to unearth the treasures.

It was with the help of the local guide ______ the mountain climber was rescued.