Some people hold the view that the new machine is advanced, while others are still skeptical _____ whether it is of practical use.

Happy birthday, Alice！So you have ________ twenty－one already!

The Students’ Union was founded for the________of them.

 If you cheat in the exam ,you could hardly ___________ it .

Since drug abusers have difficulty＿the addiction, support groups where they can talk about their struggles and find new ways to manage in the world are often needed.