The question above is incomplete, the complete version of the question is given below:
In the early days of germ theory, contagious diseases were thought to be caused by fungi or bacteria. In the 1890s, Dmitri Ivanovski filtered extracts from diseased tobacco plants and discovered that the disease could be transmitted to new plants through the filtrate. He concluded that the disease was caused by particles smaller than bacteria: the tobacco mosaic virus.
Which best explains how Ivanovski’s work led to a change in the germ theory?
A. He tried to promote his hypothesis as a law.
B. He used a new experimental method to test his hypothesis.
C. He used a more powerful bacterial strain than other scientists had.
D. He obtained results that confirmed what other scientists were thinking.
ANSWER
The correct option is B.
The germ theory of diseases states that diseases are caused by microbes. Prior to 1890s, scientists believed that communicable diseases are caused by microorganisms such as bacteria and fungi; viruses were not known during that time. The work of Dmitri Ivanovski on tobacco plant was the one responsible for the discovery of the existence of viruses. Dmitri Ivanovski was able to arrive at the results he obtained because he used a new experimental method to test his hypothesis.
