Final answer:
The nuclear envelope does not contain myosin, unlike muscle cell sarcomeres, the contractile ring during cytokinesis, and filopodia in crawling cells.
Step-by-step explanation:
The correct answer is D. The nuclear envelope.
Myosin is a protein that plays a significant role in muscle contraction. It is found in muscle cell sarcomeres, which are the functional units of muscle contraction. It is also present in the contractile ring that carries out cytokinesis during cell division, and in filopodia at the leading edge of crawling cells.
However, the nuclear envelope does not contain myosin. The nuclear envelope is a double membrane structure that surrounds the nucleus and separates it from the cytoplasm. It is primarily composed of phospholipids and proteins that help regulate the movement of molecules in and out of the nucleus.