Final answer:
Heart muscle fibers differ from skeletal muscle fibers in that heart muscle fibers are option A). shorter, connected in a tight series and branched.
Step-by-step explanation:
Cardiac muscle fibers differ from skeletal muscle fibers in several ways. Heart muscle fibers, also known as cardiac muscle fibers, differ from skeletal muscle fibers in several ways. Firstly, cardiac muscle fibers are shorter in length compared to skeletal muscle fibers. Additionally, cardiac muscle fibers are interconnected in a tight series and are branched, forming a synchronized network through intercalated discs.
This branching and interconnection allows for wave-like contractions of the heart, enabling it to function as a pump. Cardiac muscle fibers also possess many mitochondria and myoglobin, indicating a reliance on aerobic metabolism for ATP production. Therefore the correct answer is option A) shorter, connected in a tight series and branched.