Which method is commonly used for preparing a solution of known concentration?
Serial dilution is the accurate answer because it correctly identifies the biological function or role described in this question. In Water and Mole Concept, understanding the specific functions of molecules, enzymes, or structures is fundamental. Serial dilution fulfills this particular biological role through its specific structural properties, biochemical activity, or physiological mechanism. The other options (Direct weighing, Titration, and Precipitation) serve different biological functions or are associated with other processes, pathways, or structural roles within the cell or organism.
Ref: Lehninger Principles of Biochemistry, Nelson & Cox, 8th Ed., Ch. 2