If you answer every question correctly, you should get 5*20= 100.

Got 68 points, which means 100-68=32 points.

And as long as you do it wrong, you will lose points. Not only can't get 5 points, but also deduct 3 points, which is 5+3=8 points less.

32/8=4 (question) is wrong by four questions.

20-4= 16 (theme)

A: Xiao Xiao did the right thing 16.