3) Because cardiac muscles are mechanically, chemically, and electrically connected to one another, cardiac muscle tissue functions like a single enormous muscle cell. For this reason, it is called a functional .

FUNCTIONAL SYNCYTIUM

Explanation: The cardiac muscles are the Pericardium (outermost), Myocardium (middle) and Endocardium (innermost) though three(3) in number but they work as a unit,this functional unit starts with the action of the pacemaker cells,the Sinoatrial nodes,Atrioventricular nodes, bundle of his,bundle branches/purkinjes fibers.

The contraction of the heart muscles relies on impulses from the nervous system and the contraction is coordinated and rapid inorder to bring about a uniform conduction of blood into, through and out of the heart.

the correct answer to this question is #5