The breakdown of a sample of a chemical compounds is represented by the function `p(n)=300(0.5)^(n)`, where p(n) represents the number of millligrams of the substance that remains at the end of n years. Which of the following is true?
I. 300 represents the number of milligrams of the substance that remains after the first year.
II. 0.5 represents the fraction of the starting amount by which the substance gets reduced by the end of each year.
III. Each year the substance gets reduced by one-half of 300.