When did they arrive–– They ______two hours ago .They ______ here for twohours .

nspot came into its active stage last year, thathappens once every eleven years.

What do you know about Bill Gates—As far as I know，when he was a child，he showed a________of interests in everything around him

.Now all of our concentrtion is on _____ it is that the global environment will return to normal.

You played the violin wonderfully. Will you pleaseplay another _________?