The correct answer is option 'C', which is E. Jenner.

Explanation:
Immunisation or vaccination is the process of providing immunity or resistance to a disease by introducing the disease-causing microorganisms or their parts into the body in a controlled manner. The body's immune system then produces antibodies to fight these microorganisms and provides immunity against future infections.

Here is a brief explanation of how immunisation started with E. Jenner:

1. Introduction of smallpox: Smallpox was a highly contagious and deadly disease that plagued humanity for centuries. It caused fever, rashes, and pustules that left scars and could lead to blindness and death.

2. Observation of cowpox: Edward Jenner, an English physician, observed that milkmaids who had contracted cowpox, a mild disease that caused similar symptoms to smallpox, did not get smallpox. He hypothesized that cowpox protected them from smallpox.

3. Experimentation: Jenner conducted an experiment in 1796, where he took pus from a cowpox blister of a milkmaid and injected it into an eight-year-old boy, James Phipps. After the boy recovered from cowpox, Jenner exposed him to smallpox, but he did not contract the disease.

4. Development of vaccination: Jenner called this process vaccination, derived from the Latin word for cow (vacca), and continued to experiment with it. He also developed a method of preserving the cowpox virus for future use.

5. Success and adoption: Jenner's discovery was widely accepted, and vaccination against smallpox became widespread. The World Health Organization declared smallpox eradicated in 1980, making it the first disease to be eradicated by a vaccination campaign.

In conclusion, immunisation or vaccination started with the work of Edward Jenner, who discovered a way to protect against smallpox by using cowpox virus. His discovery led to the development of vaccination, which has saved countless lives over the years.