Smooth muscles are a type of muscle tissue that is typically found in the walls of hollow organs, blood vessels, and other places where involuntary movements occur. They are called "smooth" because they have a smooth appearance under a microscope, unlike skeletal or cardiac muscle tissue.

Option 1: Muscles of legs - This option is incorrect because the muscles of the legs are primarily made up of skeletal muscle tissue, not smooth muscle tissue.

Option 2: Muscles of arms - This option is also incorrect for the same reason as option 1. The muscles of the arms are primarily composed of skeletal muscle tissue.

Option 3: Stomach - This option is the correct answer. Smooth muscles are commonly found in the walls of the stomach, allowing it to contract and push food through the digestive system.

Option 4: Heart - This option is incorrect. While the heart does contain muscle tissue, it is made up of cardiac muscle, not smooth muscle.

In conclusion, smooth muscles are likely to be found in the stomach, not in the muscles of the legs, arms, or heart.