12. John wasn ' t at work yesterday. He ........................ a. must have been ill. b. must be ill. c. must have ill . d. must to be ill. 13. My father has gone away. He' ll be back .......... a week. a. for b. at c. until d. in 14. The math problem was............difficult for him.............work out. a. so / to b. too / that c. so / that d. too / to 15. ....................... don ' t visit this part of the town. a. Most tourists b. Most of tourists c. The most tourists d. Many tourist 16. What she said............... me................... unhappy. a. made / to feel b. made / feel c. made / felt d. to make / feeling 17. I haven ' t seen her for .................... that I have forgotten what she looks like. a. so long time b. a so long time c. a such long time d. such a long time 18. He is the most humorous man .............. I have ever met. a. who b. whose c. that d. which 19. Do you know all the guests ........................ to the party ? a. inviting b. invited c. who invited d. were invited GIẢI THÍCH CỤ THỂ TẠI SAO LẠI VẬY?MÌNH CẢM ƠN