Correct Option: A

ligaments (N.) : a strong band of tissues in the body that connects bones and supports organs and keeps them in position
endoderm (N.) : the inner germ layer that develops into the digestive and respiratory systems
muscles (N.) : a piece of body tissue that you contract and relax in order to move a particular part of the body
fibre (N.) : the part of food that helps to keep a person healthy by keeping bowels working and moving other food quickly through the body; roughage