He is ill today, so he stay at home.

It is _______ that he has been addicted to the drugs and has difficulty quitting it

The colors on the national flags can be ______ differently in different culture, but they have one thing in common, that is, ______of the colours was carefully chosen.

Nearly every kid hates exam , ________ it’s necessary . It helps to check if you have learned the specific knowledge .

I find this Math problem very ___ _. I believe the students can work it out .