Cells are composed of what substance that is colorless and jelly-like?

Protoplasm is the correct answer because it encompasses the contents of a cell, including the cytoplasm and the nucleus, and is identified as a colorless, jelly-like substance. It is the medium where cellular processes occur, and it is essential for maintaining the life of the cell. Protoplasm consists primarily of water, proteins, lipids, carbohydrates, and inorganic salts, contributing to its jelly-like consistency. This allows for various biochemical reactions and functions essential for the cell's survival.

Cytoplasm, while it does refer to the jelly-like fluid within the cell membrane that holds the organelles, is a component of protoplasm and is not all encompassing as protoplasm itself. Saline solution is an aqueous solution of salt, which is not a cellular component. The cell membrane refers to the structure that encloses the cell, maintaining its integrity and environment, but it is not the jelly-like substance being described. Therefore, protoplasm is the most accurate terminology for the substance comprising the cell's environment and contents.