Blood clotting involves a cascade of reactions. Which statement describes the blood-clotting process?

A. Red blood cells release clotting factors that result in the production of fibrin.

B. Clotting factors trigger the conversion of the inactive thrombin to prothrombin.

C. Insoluble fibrinogen is converted into soluble fibrin.

D. Fibrin forms a mesh that traps platelets and blood cells.

What is produced by type II pneumocytes?

A. Epinephrine

B. Elastase

C. Pulmonary surfactant

D. Alpha 1-antitrypsin

Which structural feature enables saltatory conduction?

A. Nodes of Ranvier between Schwann cells

B. Na⁺ channels under Schwann cells

C. K⁺ channels under Schwann cells

D. Sodium–potassium pumps under Schwann cells

Some strains of the pathogenic bacterium Staphylococcus aureus have developed mechanisms that protect them against foreign DNA. What effect does this have on the evolution of antibiotic resistance in these strains of S. aureus?

A. Slower evolution, as bacteria with the antibiotic resistance gene will not reproduce

B. Slower evolution, as the antibiotic resistance gene from other species will not be accepted

C. Faster evolution, as mutations within a population are less likely to occur

D. Faster evolution, as antibiotic resistance genes can only be passed to individuals of the same species

The graph shows the changing membrane potential during a nerve impulse. Which letter indicates when the potassium channels open?