How can we __________ (31) our teeth healthy? First, we ought to __________ (32)
our dentist twice a year. He can fill the small __________ (33) in our teeth before they
destroy the teeth. Secondly, we should brush our teeth __________ (34) twice a day – once
after breakfast, and once before we go to bed. We can also use __________ (35) toothpicks to
clean __________ (36) our teeth after a meal. Thirdly, we should eat food
__________ (37) good for our teeth and our body: milk, fish, potatoes, raw vegetables and
fresh fruit. Chocolate, sweets, biscuits are bad __________ (38) when we eat them between
meals. They are __________ (39) because they stick to our teeth and __________ (40) decay.
31.A. keep    B. do    C. clean    D. brush
32.A. meet    B. visit    C. look    D. find
33.A. caves    B. meals    C. holes     D. things
34.A. at least    B. at less      C. at work      D. at much
35.A. paper    B. leather    C. metal    D. wooden
36.A. on    B. among    C. between      D. at
37.   A. it is   B. that is   C. this is   D. they are
38.A. because   B. too   C. enough   D. especially
39.A. harmful   B. healthy   C. good   D. useful
40.A. fill   B. cause   C. do   D. make