Asound argument is both and
valid . . false
logical . . invalid
logical . . valid
valid . . true

The question is asking to to fill in the gaps in the sentence of ""A sound argument is both (first gap) and (second gap)". A sound argument would not be false- a false argument is of no use for us. Same holds for "invalid" - false and invalid arguments won't convince anyone because they don't hold - they are not true. So we have two options left: valid . . . true logical . . . valid now, we basically have to choose between "true" and "logical" and "logical" is better (the correct answer is the third one) since valid and true arguments are very similar, but logical tells us something about the strength of the argument (it follows a logical path)

Then what do i do after i read the excerpt? i’m not really understanding the question here.