'What does that say' challenges you on homographs.
As you will have been discovering, English has a rich range of words that look the same but can sound differently, and/or carry very different meanings, according to their context. How good are you at distinguishing between members of these pairs, or even larger groups?
You are probably most familiar with 'sound' as a noun (Answer 1) and verb (transitive as in Answer 3, else intransitive as in 'this letter sounds like the name of an insect'); among other duties, it can refer to 'sounding out' people to see what they think (as in 'un sondage' in French), which in turn refers to the deep narrow stretch of sea ~ e.g. Plymouth Sound ~ where sailors need to take regular readings ('soundings') and make sure they are not suddenly in too shallow water for safety.
The correct answer uses 'sound' as an adjective, as in 'safe and sound' (cf. the German 'gesund'); possibly suggesting that something that's healthy will 'sound' (verb!) healthy, for instance, if you tap it.