Physics can be defined as a branch of science based on:

Explanation

In summary, option B ("Experimental observation and quantitative measurement") aligns most closely with the essence of experimental physics. It emphasizes the significance of conducting experiments, making observations, and quantitatively measuring physical phenomena to gather empirical data, which forms the foundation for theories and principles in physics. The other options, while important in their own right, are not as directly related to the core idea of experimental observation and quantitative measurement in the context of physics.