There somethig wrong with the answer checker. Even it show is the answer is correct still mark it as wrong.

Answer 1

Its a bug.
Probably your internet connection is slow
that happened to me also when my connection was slow

Answer 2

Is your connection slow?

Answer 3

Oh ok then probably a bug then.

Answer 4

Its a bug for sure. Because i try an other questions and they are good.

Answer 5

My internet is good. I also try it on wifi same thing.

Answer 6

I think you forgot to add semi colon after 20.