I found a small issue with this sort or exercises: the sound of symbol is played automatically, and after that it is easy to pick a correct answer, without memorising which symbol produces this sound.

It would be more clever to play sound of every available answer.

P.S. Sorry for my English. (Screenshot of exercise: https://drive.google.com/file/d/1xMFGbszkWS2G0veCFVb6R_SlQ0cn_OyV/view?usp=sharing)