The purpose of the science of classification is to:
a) establish evolutionary relationships between organisms.
b) organize organisms according to similarities and differences

The correct answer will be option A.

Explanation:

Humans in history have always tried to organize the diversity of organism based on a number of characters like ecological functions, habit, habitat and others based on the similarities and dissimilarities.

The traditional way of classification has classified the organisms based on the morphological characters but the modern concept of a classification approach to classify the organism based on their evolutionary relationship as a grouping in this way not only organizes the animals but also conveys the information about the understanding of their evolution and evolutionary history.

Thus, option A is the correct answer.