–Why has Tom looked unhappy recently? –He has some difficulty ______ with his new classmates at school.

The space walk will last six and a half hours and the repair of Discovery is expected to __________ a little more than an hour.

 ---Many species are now in danger of dying out.----True.Measures should be______to protect them right now.

Dark glasses are sometimes worn to ________the eyes from strong sunlight.

­He         all the “ No Smoking” signs and began to smoke.