Questions: Intercalated disks are specialized connections only found in the following muscle(s): cardiac muscle skeletal muscle both none of the above

The answer is the first one: cardiac muscle.

Explanation for each option:

• Cardiac muscle: Correct. Intercalated disks are specialized structures found in cardiac muscle cells. They facilitate the synchronized contraction of the heart by allowing rapid transmission of electrical impulses between cells.
• Skeletal muscle: Incorrect. Skeletal muscle fibers do not have intercalated disks. Instead, they are multinucleated and are controlled by motor neurons.
• Both: Incorrect. Intercalated disks are specific to cardiac muscle and are not found in skeletal muscle.
• None of the above: Incorrect. Intercalated disks are indeed found in cardiac muscle.

Summary: Intercalated disks are specialized connections found only in cardiac muscle.