Antibodies

Correct Answer: A

Rationale: Antibodies are proteins (immunoglobulins) produced by B cells; secondary exposure yields a stronger response due to memory cells.

Correct Answer: A

Rationale: Group B recipients have anti-A antibodies, causing a reaction; AB are universal recipients.

Correct Answer: C

Rationale: Aldosterone retains Na+, expanding ECF and blood volume; common post-surgery.

Correct Answer: B

Rationale: Companion cells are narrow, elongated, thin-walled, living cells which are on the sides of the sieve tubes through plasmodesmata and do not have perforated cell walls.

Correct Answer: B

Rationale: Skeletal muscles or striated muscles are in the body wall and the limbs, i.e., biceps and triceps of arms, legs. The contraction and relaxation of these muscles are in the control of organism, called voluntary muscles.