Heart and kidneys are called organs, why？​

The kidneys are a pair of bean-shaped organs present in all vertebrates. They remove waste products from the body, maintain balanced electrolyte levels, and regulate blood pressure. The kidneys are some of the most important organs.

heart is actually a muscular organ. An organ is a group of tissues that work together to perform a specific function. In the case of your heart, this function is pumping blood throughout your body. Additionally, the heart is largely made up of a type of muscle tissue called cardiac muscle.

The correct answer is b