Vitamin $C$ is helpful in which of the following processes?

Growth of young cartilage takes place by

Wharton's jelly in the umbilical cord is a type of ......

Refer to the given figure and identify the correct characteristic features.
$(i)$ It is a type of loose connective tissue.
$(ii)$ It contains fibroblasts,macrophages,collagen fibres,and mast cells.
$(iii)$ The cells of this tissue are specialized to store fats.
$(iv)$ It forms the inner lining of blood vessels,stomach,and intestine.

In the body,the covering of the bone is known as

The matrix of bone is composed of