Depending on the number of variables included in the comparison, index numbers can be different. If an index number is used to measure the relative change in just one variable, this indicates a simple index. In the simple index calculation, the ratio of the two variables is converted to a percentage. In other words, index numbers are the percentage of a comparison with a reference value written without the percent symbol. It is important to determine what to write in the reference value field since the simple index calculations can be examined as a fixed based method and chain-based method. In applications, two types of indexes dominate, which are price and quantity indexes. The correct answer is B.