You have a wrong word in the question - "friend" is 친구, not 진구. The answer can be many different hings - you better give a clue in English. 친구들은 모두 학생입니다. (My friends are all students) 친구들은 모두 멋장이입니다. (My friends are all cool [ chic, dandy ])

Common speech style (formal, informal) and politeness level(casual, polite): *formal: stiff style - when addressing a multitude, or strangers. *informal: smooth style - when addressing friends, family, anyone familiar. *casual: plain - when addressing people roughly your age or younger. *polite: respectful - when addressing people who are senior to you in age/position. Examples using present tense conjugation. 이다 (is/am/are): 1) 이다: formal, casual 나는 학생이다. 2) 입니다: formal, polite 나는 학생입니다. 3) 이야/야: informal, casual 나는 학생이야. 4) 이에요/예요: informal, polite 나는 학생이에요. 하다 (do, perform): 1) 한다: formal, casual 2) 합니다: formal, polite 3) 해: informal, casual 4) 해요: informal, polite 먹다 (eat): 1) 먹는다: formal, casual 2) 먹습니다: formal, polite 3) 먹어: informal, casual 4) 먹어요: informal, polite 같다 (same): 1) 같다: formal, casual 2) 같습니다: formal, polite 3) 같아: informal, casual 4) 같아요: informal, polite

You should always provide context when asking questions^^