Question

a fibrous sac which acts as a cushion to prevent friction in a joint, between a tendon and a bone: bursa synovial fluid cartilage

Explanation:

A bursa is a fibrous - sac that acts as a cushion to prevent friction in a joint, between a tendon and a bone. Synovial fluid is a fluid in joints, not a sac. Cartilage is a connective tissue but not a fibrous sac for this specific function.

Answer:

A. bursa