1 He has developed a habit of getting up early every morning
2 When I have a difficult time learning mathematics, and he often helps me
3 There is no doubt that air pollution is a serious problem
4 This work must be completed today
5 The doctor advised her to exercise more 1 He has developed a habit of getting up early every morning
2 When I have a difficult time learning mathematics, and he often helps me
3 There is no doubt that air pollution is a serious problem
4 This work must be completed today
5 The doctor advised her to exercise more