C. it cannot be used again!
About 71 percent<span> of the Earth's surface is water-covered, and the oceans hold about </span>96.5 percent<span>of all Earth's water. Water also exists in the air as water vapor, in rivers and lakes, in icecaps and glaciers, in the ground as soil moisture and in aquifers</span>
Answer:
Rivers provide water, and a transportation route (before roads and railroads). They can also form a natural boundary or barrier to protect or defend people. Rivers can provide fish and can also make the lands around them very fertile. if they overflow their banks occasionally.
Explanation:
Two statements support the claim that Jenner has been given credit for starting and spreading the practice of immunization:
- Jenner became interested in the protective effects of cowpox during his apprenticeship. Here, we are told that Edward Jenner started working on ways to defend the body against diseases as early as during his apprenticeship when he was a teenager. He had been told that farm workers who had contracted cowpox were immune to the smallpox epidemic which was spreading across Europe at the time. He then started working on a vaccine containing cowpox.
- Jenner made the first step to erase smallpox. This first step was to try his new smallpox vaccine on a child in 1796. The child did not catch smallpox. In order to get recognition and validation from the authorities, Jenner administered his vaccine to 22 more people, with success.
