Why is los wrong? and what is the correct answer?

Es porque la oración esta en singular, si la pregunta hubiera sido plural hubiera sido así:

''Yo se los hago unos sándwiches para mi amigos''

Entonces, la respuesta correcta es: Lo.

(Creo yo)

not 7. i'd say he's 6 feet tall. if we take the average height of where sancho is from, we'd get 5'7", so, he couldn't be 5 feet, but he could be 6 feet.