Which scientist created tests that confirm that bacteria and other microorganisms cause a variety of diseases?
robert koch
anton van leeuwenhoek
louis pasteur
alexander fleming

The right answer is Robert Koch.

Microbial theory, also known as "pathogenic theory" or "germ theory," is a theory that many diseases are caused by microorganisms. Although controversial in its initial formulation, this theory was validated at the end of the nineteenth century and is now a fundamental element of modern medicine and clinical microbiology. It has led to important innovations such as the practice of preventive hygiene and the invention of antibiotics.

In 1890, Robert Koch published what has been called since the Koch (or Henle-Koch) postulates, used to determine whether a given disease is caused by given bacteria (or other microorgnaism).

The correct answer is option A, Robert Koch

Explanation:

Robert Koch conducted his first experiment to  establish a relationship between anthrax disease and its causative agent Bacillus anthracis. Before confirming his result, he conducted the  experiments for 20 generations on mice infected with anthrax disease. He used solidified liquids such as broth with gelatine and agar as a medium to grow the bacteria. He further improved his method to find the causative agents of other diseases related to microorganism. He further developed staining bacteria due to which bacteria could be seen under the microscope and this led to the identification of  bacteria’s causing tuberculosis and cholera

b

explanation:

most community's take hundreds of years to become stable