Final answer:
The correct compensatory response to decreased cardiac output is increased BP and fluid retention, due to aldosterone's role in sodium and water reabsorption and the baroreceptor-mediated increase in heart rate and contractions. The correct option is 4.
Step-by-step explanation:
Among the given options, the compensatory response to decreased cardiac output is increased BP and fluid retention.
When cardiac output decreases, the body compensates by retaining fluid and increasing blood pressure to ensure adequate perfusion to tissues.
The release of renin from the kidneys (not the liver) leads to a chain of events involving the production of angiotensin II, which stimulates vasoconstriction and the release of aldosterone.
Aldosterone causes the kidneys to reabsorb sodium and water, increasing blood volume and blood pressure.
Additionally, baroreceptors detect a decrease in blood pressure due to decreased volume and signal the heart to increase its rate and strength of contractions. The correct option is 4.