a) Manager (менеджер/управляющий), secondary (вторичный), different (различный/другой), appearance (внешность), comfortable (удобный), musical (музыкальный), tasty (вкусный), conversation (разговор), economic (экономический), recently (недавно), profession (профессия), fashion (мода), properly (правильно/должным образом), early (ранний+рано), satisfaction (удовлетворение), friendly (дружелюбный), condition (состояние).
nouns: manager, appearance, conversation, profession, fashion, satisfaction, condition.
adjectives: secondary, different, comfortable, musical, tasty, economic, early, friendly.
adverbs: recently, properly, early.
b)differ: difference, different, indifferent
comfort: comfortable, uncomfortable, discomfort
friend: friendly, unfriendly
music: musical, musically
appear: appearance, disappear
c) 1. My friend studies at the economic college.
2. They are friends and get along well with each other.
3. We live in a comfortable room.
4. You should take care of your appearance.
5. There are many different shops in this street.