Final answer:
The left ventricle has a thicker muscular layer than the right ventricle because it needs to generate greater pressure to overcome the resistance of the systemic circuit. True(A).
Step-by-step explanation:
The statement that the left ventricle has greater muscle mass than the right ventricle since it pumps against greater resistance is true(A). Both ventricles pump the same amount of blood per contraction, but the muscular layer of the left ventricle is much thicker and more developed. This is because the left ventricle ejects blood into the systemic circuit and must overcome the high resistance presented by the systemic vasculature. The needed pressure to pump blood through the large systemic circuit is significantly greater than that required for the shorter pulmonary circuit dealt with by the right ventricle. As such, the left ventricle's myocardium is significantly thicker, which is evident when comparing the muscular thickness during both relaxed and contracted states, and particularly during the ventricular ejection phase when blood is pumped into the aorta at a higher pressure than that which is generated by the right ventricle during pumping into the pulmonary trunk.