Final answer:
Cholesterol in animal cell membranes maintains fluidity and mechanical integrity, preventing too much rigidity or fluidity across temperature ranges and participating in organizing protein clusters.
Step-by-step explanation:
Cholesterol is a vital component of animal cell membranes, functioning to maintain fluidity and mechanical integrity. At various temperatures, cholesterol acts as a buffer, ensuring that the membrane remains sufficiently fluid for proper cellular function. It prevents the membrane from becoming too rigid in cold temperatures and too fluid in warm temperatures. Furthermore, cholesterol contributes to the organization of transmembrane proteins into lipid rafts, adding to the mechanical integrity of the cell membrane. The correct answer to the question is A: Fluidity, mechanical integrity.