This long muscle lies obliquely across the anterior thigh. It allows you to sit in a crossed-leg (lotus)position. It flexes the leg at the knee and abducts and laterally rotates the thigh at the hip. A) Hamstrings
B) Quadriceps femoris
C) Sartorius
D) Gastrocnemius

it's C

Explanation:

The sartorius muscle is the longest muscle in the human body. It is a long, thin, superficial muscle that runs down the length of the thigh in the anterior compartment. The name Sartorius comes from the Latin word sartor, meaning tailor, and it is sometimes called the tailor's muscle.

it would be heredity