Doing/to Do It.
This quiz focuses mainly on which verbs are followed by TO DO, and which are followed by DOING. It can be a fun way, especially if you use the timer, to learn when to use each form. Once you have learned the difference, do the accompanying quizzes that focus on the meaning of the main verbs.
The timer gives you 15 seconds to find the answer. It notes your errors but it only shows you the correct answers at the end.
If you don't use the timer you see the correct answers immediately and, in many cases, you can click on More Feedback to see a similar word or sentence.