C# training has an issue i cannot proceed

Question

This lesson cannot accept the good answer which can be a char: good answer ‘a’. Also the other wrong answers is not accepted ( i have tried it. What should i do

Answer 1

Check whether the quiz is expecting more than one right answer. If there are checkboxes, it may be expecting more than one of them to be checked.

Answer 2

Further to Brian's correct response, also check your internet connection. If you're on WiFi, try using your phone's internet for submitting or the other way around, or try a different WiFi altogether.

Answer 3

as I see, there are 5 choices, all with checkbox, not with radio button.
and read carefully the task as well :-)