The main purpose of the text is to______.A．convin

The main purpose of the text is to______.

A．convince the reader that vaccines are not as safe as many think

B．educate the reader on how vaccines are used and some of their dangers

C．educate the reader on the circumstances that would neccesitate widespread vaccinations

D．present the method by which vaccines are used through the case of the smallpox vaccine

请帮忙给出正确答案和分析，谢谢！