Final answer:
The quadriceps femoris has four heads: rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius, which work together to extend the knee.
Step-by-step explanation:
The quadriceps femoris is a muscle group located on the anterior thigh, consisting of four heads: the rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius. These muscles work together to extend the knee.
The term 'quadriceps' derives from Latin, with 'quadri-' meaning four and '-ceps' coming from 'caput' which means head. Therefore, the quadriceps femoris has four heads, and the correct answer to the question is option 4) Four.