In addition to cells, what can tissues be made of?

Tissue is made of more than one cell. In tissue, cells are made od same type of cell which performs a particular function. When many tissues combine together it forms an organ.

For example, heart is also formed from tissues which function is to pump blood from heart to all parts of the body. In muscles, the tissues which is present are responsible for the movement of muscle and movement of organisms from place to place.

the correct answer: the index of refraction of the second medium is lower i tried this persons answer and it was wrong this person is lying

the answer is:

carbon dioxide