question 3 is confusing, because it mentions parts are in "pairs", and I don't see how they are paired at all. I don't really understand the question. But, maybe what they're looking for is a GROUP BY on the CLASS column.
I think they use the word pair, because there's more than one item in each class. For example, there's not one, but 3 items in class HW (Iron, Cordless Drill, Stand Mixer)... and for some twisted reason, they call that a pair, I guess.
This is what I came up with and hopefully it's what's wanted...
SELECT PART_NUM, DESCRIPTION, CLASS
FROM PART
GROUP BY CLASS
ORDER BY CLASS;