Final answer:
Option C, which indicates that an increased blood volume leads to the expansion of the periphery, is the correct answer as hydrostatic pressure increases with blood volume, pushing fluid into peripheral tissues.
Step-by-step explanation:
The hydrostatic effects of water in terms of blood volume and what happens to the periphery of the body to the thorax involve the balance between hydrostatic pressure and osmotic pressure. Hydrostatic pressure is the force that blood exerts against the walls of blood vessels, and it tends to push fluid out into the interstitial spaces from the capillaries. In response to decreased blood volume, baroreceptors detect a drop in blood pressure and signal the heart to increase its rate and/or strength of contractions, momentarily compensating for the pressure decrease. Fluid movement between compartments, due to hydrostatic pressure, can result in the expansion of the peripheries when the hydrostatic pressure in blood vessels exceeds the opposing osmotic pressure, pushing plasma and nutrients out of the capillaries into surrounding tissues.
In regards to the specific scenarios provided in the question, increased blood volume will increase hydrostatic pressure, which could lead to the expansion of periphery as fluid is pushed out into the tissues from the capillaries. Hence, option C which states 'Increases blood volume; expansion of periphery' is the correct answer. This is supported by the understanding that as blood volume and therefore blood hydrostatic pressure increase, they promote filtration and movement of fluid into peripheral tissues, causing them to expand.