By the year 2020 scientists _____ a lot of research on AIDS

Ninety-six point five percent of the water on the earth ______ sea water.

Of the two sisters, Betty is______one, and she is also the one who loves to be quiet.

He has been working hard for 6 days，________a lack of concentration in the meeting.[ ]

Which country has________population ,China , India orAmerica— China.