What chemical process converts nutrients into energy for the body to store?

Metabolism is the correct choice because it encompasses all the biochemical processes involved in converting nutrients from food into energy that the body can use and store. This includes both the breakdown of nutrients to release energy (catabolism) and the use of that energy to build and repair cells and tissues (anabolism).

Understanding metabolism is crucial in the context of nail technology because knowledgeable practitioners can better advise clients on how dietary habits may impact the health of skin and nails. For instance, certain vitamins and minerals play key roles in nail growth and strength, and metabolism is the process that ensures these nutrients are effectively converted into usable energy and materials for the body.

The other choices relate to important aspects of the body's functions but do not directly address the conversion of nutrients into energy. Digestion refers to the mechanical and chemical breakdown of food into smaller components that can be absorbed. Absorption involves the transfer of nutrients from the digestive tract into the bloodstream. Circulation relates to the movement of blood throughout the body, delivering those absorbed nutrients to cells but does not itself convert nutrients into energy.