I find this Math problem very ______. I believe students can work it out ______.

On the night of February 14th, 2011, all the Chinese _________ by Guo Mingyi, a very common worker who ________ more than 180 poor children since 1994.

There is usually ________ in summer in Yangzhou, it helps crops(庄稼) grow well.

I study for a test ______ working with a group. [ ]

The volunteers __ a lot of help to the community for nearly ten years.