forced answer + score

You can force a student to proceed until he has given a correct answer, counting each try. As explained in an earlier worksheet you can achieve this by showing the button next exercise only if a correct answer is given.

What kind of score or eventually no score at all...

Of course such a score doesn't tell if the difference between the two values is due to a lot of wrong answers in just a few exercises or to regular wrong answers in a lot of exercises. No option is the absolute best. It also depends on the students. One student can be eager to reach a high score and be stimulated by applets wit a score. A second student might like applets with tips or the possibility of showing the answer and be stimulated by applets without any score at all... It's up to you to experiment with different options, eventually in a different way in different classgroups.