The correct answer is a) the meaning of life. The explanation of this question: what is the purpose of life? Implies approaches from a philosophic point of view demand qualitative methods to obtain an answer and cannot be measured using statistical analysis. The traditional scientific approach (the scientific method) states that “what cannot be measured (using mathematics) is subjective, thus not reliable nor comparable. All the other options: b) the extent of, c) a range and d) a pay gap can be express in continuous numerical variables, in opposition to the option a).
Nevertheless, nowadays a combination of methods (mixed methods) using variations of quantitative and qualitative Technics is being accepted, as positivism (from where the traditional scientific method come) has failed to answer many of the essential questions’ humans have. it is not just useful to know "how many?" but "why?" most of the times, a combined answer is preferable than only a number (and perhaps more correct)
A recommendable bibliography if you want to go into deep is: Creswell, J. (2009). Research design: Qualitative, quantitative, and mixed methods approaches (Laureate Education, Inc., custom ed.). Thousand Oaks, CA: Sage Publications.
Greetings!
