Question

the heart is...
only a muscle.
both a muscle and an organ.
neither a muscle or an organ.
only an organ.

Explanation:

The heart is made of cardiac - muscle tissue and is an organ that pumps blood throughout the body. It fits the definition of both a muscle (due to its muscle - like properties) and an organ (a group of tissues working together for a specific function).

Answer:

both a muscle and an organ.