Which is the best description of a change in society that has resulted from advances in understanding the causes of diseases?

The best answer to the question stated above is letter B.
 Improved methods of sanitation best describes the  change in society that has resulted from advances in understanding the causes of diseases.

Choices to this question are:
A. An increased number of hospitals
B. improved methods of sanitation
C. improved use of microscopes
D. increased wages for healthcare workers.

Velocity is the speed of an object in a certain direction so you'd need to know speed and direction