The correct answer is: D. Fundamental research.
Fundamental research is a type of research that is concerned with understanding the basic principles of nature. It is often conducted in universities and research institutes, and it is not directly aimed at solving any practical problems. Instead, fundamental research is motivated by a desire to understand the world around us.
Quantitative research is a type of research that uses numerical data to answer questions. It is often used in the social sciences, such as psychology and sociology. Quantitative research can be used to describe, explain, and predict phenomena.
Qualitative research is a type of research that uses non-numerical data to answer questions. It is often used in the humanities, such as history and philosophy. Qualitative research can be used to understand the meaning of human experiences.
Applied research is a type of research that is aimed at solving practical problems. It is often conducted in industry and government, and it is closely related to development. Applied research can be used to develop new products, improve existing products, and find new ways to do things.
In conclusion, fundamental research is the type of research that is concerned with describing, explaining, and predicting natural phenomena and relies only on experience and observation.