Answer:
Isotopes measured in speleothems can most directly tell scientists about:
c. The source region of water that contributed to rainfall in a region
Step-by-step explanation:
Speleothems, such as stalagmites and stalactites, form in caves from mineral-rich water dripping or flowing. Isotopic analysis of oxygen and hydrogen in these speleothems can provide insights into the source region of the water that contributed to rainfall in a specific region, which can in turn provide information about past climate conditions and precipitation patterns.