He is really an excellent doctor and he is____to becoming an expert in this field.

The experiment shows that proper amounts of exercise,if _____ regularly, can improve our health.

I don’thave a partner to practice English_____. –Why not join an Englishlanguage club to practice_____

It is said that many kids are worried about the year 2012, ____they think the earth will be destroyedby disasters [ ]

This is the very spot ___________gold was discovered long ago