Read the following passage and choose the best answer (A, B, C, D):
Human beings are plagued by all kinds of diseases and millions of people die from them. Many of these diseases such as diabetes, polio, whooping cough and diphtheria can be fatal and in the past, people used to die from them. However, with modern technology and a lot of research, scientists and doctors have come up with various ways to cure these diseases, and consequently, many lives are saved. In doing the medical research, doctors have come face to face with many problems. One such problem is the opposition that comes from animal activists. They are against the inhuman treatment of animals. They argue that in conducting their medical research, doctors put animals through a very painful process and this should be stopped. According to the fiercest animal activists, nothing justifies the use of animals in medical experiments, even if lives might be saved. To get their message across, animal activists are even willing to resort to the use of violence. Many animal protection groups, like the Animal Liberation Front (ALF), have broken into laboratories illegally to ‘rescue’ animals. They take away whatever animals they can find and free them. These people also make their case by threatening the researchers. They vandalize medical equipment, and in the most serious cases, they even . In stealing the animals, the activists are actually hindering the progress of medicine. In many cases, the animals were part of research for the cure for various diseases and visual defects in babies. Cures for problems that people face, therefore, come slower and in the waiting period, more people die. Researchers have come up with many cures in the process of working with animals and on animals. Organ transplants are so common today, but we forget that they became only possible after they were tested on animals. Doctors were able to come up with a cure for river blindness, a disease that affects millions of people in South America and Africa. These are only a few examples, and there are many more. In spite of what animal activists think, most researchers do not treat animals cruelly. In fact, mistreated animals which are in agony will affect the quality of research so that results obtained are not really reliable. Thus, researchers do try to treat animals as well as possible. In the long run, animal activists can cause serious damage to the future of medicine. With their persistent campaigning, much of the public supports their cause. People with AIDS or cancer need doctors to do research to save their lives, and often it is a case where animal research is crucial before any cure can be found
4. Thanks to tests on animals, doctors succeeded in ____
