题目选项分析

Just as Edward Jenner used the pustules from milkmaids to inoculate against smallpox, effectively removing the specter of death that had hung over the population, so modern immunologists have obtained the live virus in the pustules of infected organisms, from which the smallpox vaccine is derived

Just as Edward Jenner used the pustules from milkmaids to inoculate against smallpox, effectively removing the specter of death that had hung over the population, so immunologists today use the pustules of infected organisms to obtain a live virus from which the modern smallpox vaccine is derived