Which organ filters blood and stores platelets?

Correct Answer: B

Rationale: The spleen filters blood and stores platelets; thymus matures T cells, nodes filter lymph, tonsils trap pathogens.

Correct Answer: B

Rationale: Sinusoids supply red pulp; central arteries feed white pulp, veins drain, capillaries are elsewhere.

Correct Answer: B

Rationale: Artificial active immunity comes from vaccines; natural active is from infection, passive (C, D) is from antibodies.

Correct Answer: B

Rationale: Red pulp removes old RBCs; antibodies are white pulp, T cells are thymus, lymph is nodes.

Correct Answer: C

Rationale: Tolerance prevents self-reaction; hypersensitivity is overreaction, autoimmunity is self-attack, immunodeficiency is weakness.