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5. The question couldn't be answered because it was very hard.  
6. It is not easy to speak English fluently.
7. Working in that condition was impossible.
8. The film was so boring that I fell asleep.
9. I'm not rich enough to take a space trip.
10. He isn't tall enough to be a good goalkeeper. 
11. The film was so good that I didn't want to turn the TV off.
12. He spoke too quickly for me to understand what he said. 
13. He is not old enough to see the horror film.
14. He climbed the tree so that he could get a better view.
15. You'd better go to work today.

16. It takes me half an hour to traveling to work by motorbike everyday.
17. Chocolate makes some people come out in spots.
18. I am going to get my roof mended by the builder tomorrow.
19. Mary went to the library so as to borrow some books.

5 The question couldn't be answered because it was very hard
6 It is not easy to speak English fluently
7 Working in that condition was impossible
8 The film was so boring that I fell asleep
9 I'm not rich enough to take a space trip
10 He isn't tall enough to be a good goalkeeper
11 The film was so good that I didn't want to turn the TV off
12 He spoke too quickly for me to understand what he said 
13 He is not old enough to see the horror film
14 He climbed the tree so that he could get a better view
15 You'd better go to work today
16 It takes me half an hour to traveling to work by motorbike everyday
17 Chocolate makes some people come out in spots
18 I am going to get my roof mended by the builder tomorrow
19 Mary went to the library so as to borrow some books