听力原文： This is Vaccination Week in the Americas, The Pan American Health Organization a

nd officials from the United States, Mexico and Canada launched the campaign Monday. Public health officials say they hope to reach forty-four million children and adults throughout North, Central and South America. The children will be vaccinated against measles, polio, rubella and other diseases that can be prevented.

Officials say vaccines have greatly reduced child deaths and disability caused by preventable diseases in the Americas. This month marks the fiftieth anniversary of the Salk vaccine against polio. Today the Americas have been declared polio-free. Smallpox has been ended worldwide. And there has been progress against measles. Health officials in the Americas are also working to end another disease, rubella, through vaccination.

Eleven thousand babies are born each day in the United States. Public health officials say children should be vaccinated against twelve diseases before age two. But they say more than twenty percent of two-year-olds in the United States are not fully protected against these preventable diseases.

All thirty-five countries in North, Central and South America are members of the Pan American Health Organization, It is based in Washington. It was established in 1902 and represents the Americas in the World Health Organization.

The Vaccination Week campaign was launched ______.

A．Monday

B．Tuesday

C．Wednesday

D．Sunday