The right answer is C.
A bar chart, also known as bar graph or column diagram, is a way to graphically represent a set of data or values, and is made up of rectangular bars of lengths proportional to the values represented. Bar graphs are used to compare two or more values. The bars can be oriented horizontally or vertically.
Since the value obtained at very low concentration (30) is twice the value obtained at average concentration (15), it can be deduced that "C" is a correct answer. The other answers are false.
