Answer:
muscle
Step-by-step explanation:
The heart is a muscle that pumps blood throughout the body. It is the strongest muscle in the body, and it can be made stronger through exercise.
The other options are not correct:
A. gland: A gland is an organ that produces and secretes a substance, such as hormones or enzymes.
C. nerve: A nerve is a bundle of nerve fibers that transmit signals from the brain and spinal cord to the rest of the body.
D. organ: An organ is a group of tissues that work together to perform a specific function.