The correct answer is option 1, the Sartorius muscle. The Sartorius muscle is the longest muscle in the human body. It is a long, thin muscle that runs from the outer hip bone to the inside of the knee. This muscle helps to flex and rotate the hip and knee joints. It is named after the Latin word "sartor," which means tailor, because in a seated position the muscle is shaped like the position a tailor would sit in while sewing.

Option 2, the Masseter muscle, is not the longest muscle. It is a strong muscle in the jaw that helps with chewing.

Option 3, the Stapedius muscle, is the smallest muscle in the human body. It is located in the middle ear and helps to dampen excessive vibrations.

Option 4, the Gluteus Maximus muscle, is the largest muscle in the human body. It is located in the buttocks and helps with hip extension and external rotation.