Final answer:
Titin is the protein that links thick filaments to the Z line in muscle sarcomeres, playing an important role in muscle elasticity and stability.
Step-by-step explanation:
The protein that links the thick filaments to the Z line is titin (C).
In muscle structure, titin serves as an elastic molecule that connects thick filaments of myosin to the Z line structure in a sarcomere, which is the basic unit of muscle contraction. Troponin (A) and tropomyosin (B) are regulatory proteins that are part of the thin filament system and play critical roles in muscle contraction by regulating the interaction between actin and myosin.
Nebulin (D) is a giant protein that is thought to play a role in stabilizing and aligning actin filaments in the sarcomere and is associated with the thin filament. Myomesin (E) forms part of the M line and provides structural stability to the thick filaments. Titin is responsible for the passive elasticity of the muscle and connects each thick filament to the Z line.