单选题
[填句补文]Some 20，000 tons of antibiotics are used in the European Union and the US each year. More than half are give to farm－animals to prevent disease and promote growth. ________.
A、The warning comes from a researcher in Switzerland who looked at levels of the drugs in farm slurry.
B、The drugs could be getting into our food and water.
C、Many drugs given to humans are also excreted unchanged.
D、But recent research has found a direct link between the increased use of these farmyard drugs and the appearance of antibiotic－resistant bugs that infect people.
正确答案：D
答案解析：前两句讲的是抗生素在欧洲和美国的大量使用，这句讲的是由此导致的不良后果，接上去是最合理不过的。But明确地表明了这一转折。