Question

Three things are necessary for humans to keep their balance while walking on two legs.

Answer 1

Um well
Legs
Feet
Strength 

Answer 2

Question; Three things are necessary for humans to keep their balance while walking on two legs.

The head should be positioned in the  

⇒ middle, center of the body.

The weight of the  

⇒ upper body should be over the pelvis.

The  

⇒ legs, knees need to be stable enough to support the body's weight.