In a tube of centrifuged blood, the order of substances from top to bottom would be:

Correct Answer: C

Rationale: Centrifuged blood layers: plasma (top), buffy coat (WBCs/platelets), RBCs (bottom, C).

Correct Answer: A

Rationale: Type A (A) has A antigen, anti-B antibody.

Correct Answer: B

Rationale: RBCs are ~99% of formed elements, not 10% (B); other statements (A, C, D) are true.

Correct Answer: D

Rationale: Universal recipients (AB+, D) have A/B antigens, no antibodies.

Correct Answer: C

Rationale: Vasodilation widens the vessel, reducing resistance slightly (C) per Poiseuille’s law (resistance ∝ 1/radius⁴). Increase (A, B) occurs with constriction, huge decrease (D) overstates it.