How are you with your new classmates? —We often help each other

Most whales must come up for air after several minutes, _______ a few can stay under water for an hour or more

Please make sure that no details _____ before youdeliver a speech

In many countries, some scientistsare already _______ research in order to produce a cloned human baby.

16．—Where is Lily, Lucy? I cannot find her anywhere. —She_________have been off long. I saw her clean the window just now.