Afecțiuni is also correct seeing as we DON'T have a context for the sentence we're supposed to fill in.
No wonder their diagnosis is fast and cheap, if they ask the patient to self diagnose. I'd rather receive it with a healthy skepsis
both variants are correct and should be accepted as correct :
1 ) ce afectiune ( sing.) crezi ca ai
2 ) ce afectiuni (pl. ) crezi ca ai