Most of the ancient Chinese scientific works are empirical summaries, not theoretical discussions. The inventions described are designed to solve practical problems in national and social life, rather than trying to achieve major breakthroughs in a certain research field. In terms of research methods, Chinese science and technology attaches importance to comprehensive and holistic research, rather than grasping things as a whole, rather than separating research objects from the intricate connections, independently studying their entities and attributes, and exploring their mysteries in detail. Science and technology in ancient China did not develop to a higher level. What does this paragraph focus on the explanation of? ['Defects in research methods have long stagnated ancient Chinese science and technology.', 'Solving practical problems is the driving force for the development of ancient Chinese science and technology.', 'The focus of scientific research in ancient China and its historical background.', 'The root cause of the lack of progress in science and technology in ancient China.']