Medical researchers in Boston recently found out【C1】______ millions of people already knew: drinking is good for you. The doctors【C2】______ up with the following ideas and suggestion: one【C3】______ six drinks is good for you;【C4】______ drinking, or seven to thirteen drinks a week is not good; but having【C5】______ than thirteen drinks a week is downright【C6】______ because drinking too much wine could cause dementia, an illness that can【C7】______ your brain,【C8】______ your ability to drink or act normally.
【C9】______ more than 300 senior citizens over many years, a group of researchers【C10】______ that a few drinks a week is good for you【C11】______ it prevents hardening of the arteries, a major【C12】______ to such cardiovascular(心血管的) problems【C13】______ heart attacks and strokes. Strokes, especially, are a major【C14】______ of non-genetic dementia,【C15】______ occurrence may be reduced by【C16】______ amounts of alcohol.
Doctors pointed out that,【C17】______ hearing this news, older adults should not rush out to buy six【C18】______. Those who drank in the【C19】______ were long time drinkers. Any new user of alcohol should first【C20】______ a physician, they cautioned.
【C1】

A. what
B. which
C. that
D. why