37 Unless you don't eat an apple a day , you won't stay healthy
38 Unless you stop wasting it, you will run out of money
39 Don't call me if it isn't an emergency
40 If James doesn't study harder , he won't pass the test
41 Unless Jane doesn't finish her work before 6pm , she will dine out with her friends
42 Unless he stays healthy , my brother won't go travelling this summer
43 It is difficult to do these exercises, if you don't listen attentively to the teacher.