How about a "Second Chance" option?
Sometimes I oversee that the plural is asked and so my answer is wrong. Could there be an option like a "Second Chance" so that you are informed that you have typed in some minor mistake and get the possibility to correct the answer? Also sometimes I miss the plural s on my keyboard and so I loose a heart, that feels kinda unfair. Would be nicer to get the chance for correcting myself instead of just the message that I'm wrong.