单选题：根据以下材料回答第题：Sugarless yoghurt (酸奶) could help beat bad breath

根据以下材料回答第题：
Sugarless yoghurt (酸奶) could help beat bad breath, tooth decay and gum disease, say scientists. Japanese researchers found eating the yoghurt（1）levels of hydrogen sulphide (硫化氢) —a major（2）of bad breath — in 80%of volunteers.The（3）are active bacteria in yoghurt.
Details were（4）at a meeting of the International Association for Dental Research. A(n)（5）of 24 volunteers who participated in the study were given strict instructions（6）oral health, diet and medicine taking. They spent two weeks（7）yoghurts and similar foods, like cheese.Researchers then（8）bacteria levels and odor-causing compounds,（9）hydrogen sulphide. The volunteers then ate 90 grams of yoghurt a day for six weeks.
At the end of the study, researchers took（10）again. They found hydrogen sulphide levels（11）in 80% of participants.
Dr. Nigel Carter, chief executive of the British Dental Health Foundation, said: "The foundationhaslongbeen（12）people's attention to sugar-free yoghurts as a healthy snack, so it is pleasing to hear that it may have oral health benefits we were previously（13）of. "
"Although this research is still in the early stages there is no（14）that sugar-free yoghurts provide a much healthier（15）to sweets and chocolate, and we would encourage snackers to（16）them into their diet. "
（17）, Dr.Carter stressed that the best way to beat bad breath was by（18）a good oral health routine. This involves brushing twice-a-day with fluoride ( 氟化物 )toothpaste, cutting（19）on the frequency of sugary snacks and drinks and visiting a dentist（20）.
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