Spot the misspelling
Reading a spelling is a different skill from producing one, so here the names are given to you and something is wrong with them.
Sometimes a name is missing and you name the gap. Sometimes one name is spelled wrong — and a wrong name is always the RIGHT LETTER with the wrong accidental, because that is the mistake people actually make.
C major shown as C, E♭, G has the right three letters. Only the accidental betrays it. Tap the intruder.
Right letter, wrong accidental — or one name missing
C major should be C, E, G. The E♭ is the intruder — tap it.
Practise this in the trainer — it opens with this lesson the first time the concept comes up.