根据以下材料，回答1-20题
Many Americans have been feeding a baby aspirin once a day, believing it would protect them from a heart attack, a stroke,and even cancer.But several recent studies have 1 this into question.
One large-scale study 2 more than 19,000 healthy people ages 65 and older.Participants were 3 assigned to take either 100 mg of aspirin (slightly more than the 81 mg dose that 4 people take) or a placebo (aharmless substance given to a sick person 5 medicine, without telling them it is not real) every day for an average of 4.7 years. 6 did people in the aspirin group not 7 their risk of heart disease,dementia, or disability, but they were also more 8 to suffer from significant bleeding in the digestive tract or brain.And they were more likely to die 9 , apparently because of an increased risk of 10 cancer.
11 , a trial of more than 12,500 people ages 55 and older 12 to have a moderate cardiovascular risk found no benefit to taking aspirin daily.In a study of more than 15,000 people with diabetes, a daily aspirin did 13 heart attacks and strokes, but it also 14 major bleeding.And according to an analysis of data from more than 117,000 people, 15 people needed larger doses of aspirin to help 16 their risk of heart attack, stroke, and cancer.
The bottom line：Although there is good 17 that aspirin can help people who have already had or are at 18 risk for heart attacks or strokes, the drug's 19 is not so clear for people,especially older people, with less risk. 20 your doctor before starting—or stopping—aspirin.
第14题答案是

A resulted

B led

C influenced

D caused