A. please B. insignificant C. exploit D. skilful A. subject B. blackboard C. obligation D. postcard A. don't B. atlas C. OK D. Christmas Eve A. actual B. rubber C. ow D. incumbent A. professor B. cause C. ask D. sorry A. listen to B. purity C. tableland D. gray A. parrot B. sudden C. cameraman D. blunt A. door B. plug C. having class D. transport A. everybody B. come in C. less and less D. rocket A. doorbell B. window C. taught D. make a list