Neighboring cardiac muscle cells in the walls of heart chambers have specialized cell-to-cell contacts that electrically and mechanically link the cells together, permitting the immediate passage of muscle impulses. these cell-to-cell contacts are called

Neighboring cardiac muscle cells in the walls of heart chambers have specialized cell-to-cell contacts that electrically and mechanically link the cells together, permitting the immediate passage of muscle impulses. These cell-to-cell contacts are called intercalated discs.

Explanation:

Intercalated discs can be described as unique structures present between the cardiac muscles of the heart. The intercalated discs play a major role in making the cardiac muscles contract in a rhythm so that the heart can pump blood in a regular fashion and it hence regulates the effective functioning of the heart. The intercalated discs are the structures that join on cardiac muscle to another and is involved in the transmission of chemical messages between them.

chert is a sedimentary rock composed of microcrystalline or cryptocrystalline silica. with this little bit of information, you can come to the conclusion that your answer is c.  

explanation:

a covalent bond, specfically triple bond