5.  Choose the word (a, b, c, or d) that best fits each of the blank spaces.
How can we keep our teeth (21) ______? Firstly, we ought to visit our (22) ____ twice a year. Secondly, we should brush our teeth (23) ____ a toothbrush and fluoride toothpaste at least twice a day, once after breakfast and once before we go to bed. We can also use toothpicks (24) _____between our teeth after a meal. Thirdly, we (25) ______ eat food that is good (26) ______ our teeth and our body: milk, fish, brown bread, raw vegetables, fresh fruit, etc.
21. a. health     b. healthy  (adj +N )  c. healthily    d. unhealthy
22. a. dentist     b. doctor    c. teacher    d. engineer
23. a. on     b. of    c. by    d. with ( đánh răng = bàn chải )
24. A. clean    b. to clean  ( để làm sạch )  c. cleaning    d. to cleaning
25. a. should    b. ought to    c. need    d. a & b ( nên )
26. a. for  ( good for : tốt cho )  b. at    c. on    d. to