听力原文： The first significant step in the fight against infectious disease Was made in 1

796 with discovery of a vaccine to prevent smallpox by Edward Jenner. Jenner had become aware of the fact that milkmaids who had suffered from a mild illness, cowpox, were unlikely to catch the much more serious smallpox disease. Jenner experimented on a child, introducing cowpox into the bloodstream. Later, the child was inoculated with smallpox, but did not catch the disease. Jenner's method had, proved much safer than the fashionable technique of inoculation, which had been brought to Britain from Turkey by Lady Montague. Despite opposition from the medical establishment, many of whom made a good income from inoculation, the government backed Jenner's claims; by 1853, vaccination had become compulsory for infants.

Louis Pasteur was a French chemist who in 1867 was able to demonstrate for the first time that germs caused disease. Pasteur went on to develop vaccines for chicken cholera, anthrax and rabies. The new science of bacteriology was advanced further by a German scientist, Robert Koch. Using microscopes and innovative methods of staining germs, Koch was able to identify specific germs as being responsible for the cause of disease. In 1882-3, he identified the microbes responsible for tuberculosis (TB) and cholera.

A rivalry developed between Pasteur and Koch, based in part on the tension which existed following France's defeat in the Franco-Prussian war of 1870-1. Both scientists were recognized in their own countries for their work, and set up with research centers. In 1881, Pasteur, successfully tried vaccine which protected against anthrax in animals. Koch, who quickly heard of the breakthrough by telegram, attempted unsuccessfully to discredit Pasteur. When, in the following year, he had the opportunity to treat a boy with rabies called Joseph Meister, Pasteur succeeded in developing a rabies vaccine.

What was the first step in fighting against infectious disease？

A．The discovery of a vaccine.

B．A powerful injection.

C．The help of a milkmaid.

D．The help from government.