1.happy-happily(adv)
2.comfort-comfortable(adj)-comfortably(adv)
3.person-personal(adj)
4.inform-informal(adj)-information(n)
5.love-lovely-lover
6.furnish-furniture(n)
7.birth-?(no word form)
8.class-classic-classical
9.amaze-amazing(adj)-amazement(n)
10.good-goodly-goodness-goods
11.bad-badly-badness-?
12.luck-lucky-luckily-luckless-?
13.old-?-?-?-?