Which letter from the following image represents the white blood cell subtype that includes B and T cells?

A. Mastication: Mechanical digestion involves physically breaking down food into smaller pieces, and mastication is a prime example of this.

B. Absorption: This is the process by which nutrients pass from the digestive system into the bloodstream, not a form of mechanical digestion.

C. Catabolism: Catabolism refers to chemical processes that break down molecules within the body, not mechanical digestion.

D. Anabolism: This refers to the synthesis of complex molecules from simpler ones, not related to the physical breakdown of food.

A. Increased afterload: Increased afterload, the resistance the heart must overcome to eject blood, typically reduces stroke volume because the heart has to work harder to push blood against higher pressure.

B. Decreased heart contractility: This would reduce stroke volume, as the heart would be less effective at pumping blood.

C. Increased preload: Preload refers to the volume of blood in the ventricles at the end of diastole. An increased preload stretches the heart muscle, which typically leads to a stronger contraction and higher stroke volume.

D. Decreased blood pressure: While low blood pressure may reduce afterload, it doesn't directly increase stroke volume unless other factors are at play.