阅读理解。
阅读下列短文，从每题所给的四个选项 （A 、B 、C 和 D ）中，选出最佳选项。
In an ideal world, people would not test medicines on animals. Such experiments are stressful and sometimes painful for animals, and expensive and time-consuming for people. Yet animal experimentation is still needed to help bridge vast gaps in medical knowledge. That is why there are some 50 to 100 million animals used in research around the world each year.
Europe, on the whole, has the world's most restrictive (严格的) laws on animal experiments. Even so，its scientists use some 12 million animals a year, most of them mice and rats, for medical research. Official statistics show that just 1.1 million animals are used in research in America each year. But that is misleading. The American authorities do not think mice and rats are worth counting and, as these are the most common laboratory animals, the true figure is much higher. Japan and China have even less comprehensive (全面的) data than America.
Now Europe is reforming the rules governing animal experiments by restricting the number of animals used in labs. Alternatives to animal testing，such as using human tissue or computer models, are now strongly recommended. In addition, sharing all research results freely should help to reduce the number of animals for scientific use. At present, scientists often share only the results of successful experiments. If their findings do not fit the hypothesis (假设) being tested, the work never sees the light of day. This practice means wasting time, money, and animals' lives in endlessly repeating the failed experiments.
Animal experimentation has taught humanity a great deal and saved countless lives. It needs to continue，even if that means animals sometimes suffer. Europe's new measures should eventually both reduce the number of animals used in experiments and improve the way in which scientific research is conducted.
表示一种运算符号，如果x 
1= ：