By definition, a synonym is a term used to describe a given word in which it has exactly the same meaning to the other word, regardless of its spelling. Therefore, the properly matched word pairs would be:
1. deserter = renegade
2. distant/cool = aloof
3. quarrelsome = pugnacious
4. serfdom = feudalism
5. plot = conspire
6. boyfriend = beau
7. glorify = exalt
8. change = transfigure
9. confuse = befuddle
10. indifferent = nonchalant