Some fruits are sweet. No sweet thing is sour. Which conclusion follows?
Correct: B
From 'Some F are S' and 'No S are O' (where O = sour), we can conclude 'Some F are not O' — that is, some fruits are not sour. This follows because the particular fruits that are sweet cannot be sour (since no sweet thing is sour). The conclusion 'Some fruits are not sour' is valid. The other options either reverse relationships or contradict the premises.