How can reduced precipitation lead to limited water availability?

Reduced precipitation leads to limited water availability because water catch basins or reservoirs tend to dry out. When it dries out, people tend to start using and drying out the back up water sources and stored ones. Until such time, that the sources of water will totally dried out.

C. it comes from the core of the earth.

Answer;

hot magma rises and pushes up toward the lithosphere, and as it cools it cycles back down toward the core to be heated again.

explanation; convection currents are the circular pathways taken by a fluid that enhances heat transfer by the process known as convection which occurs in fluids.convection currents transfer heat from one place to another by mass motion of a fluid. earth mantle is in a semi-liquid state and behaves like any other fluid, rising up from the bottom of the mantle after becoming hotter and less dense from heat of the earth's core, as the rock loses heat into the earth's crust it becomes cooler and more dense, then sinking back down to the core, then repeating the cycle.