The correct answer is Ribosome. Explanation & Key Takeaways: Cell • The cell is regarded as the structural, functional, and biological unit of all organisms. • It is a membrane-bound structure containing compartments and structures dispersed in the cytoplasm. • There are two types of cells based on the presence of cytoplasmic membrane-bound organelles: eukaryotic cells and prokaryotic cells. • The presence of membrane-bound organelles characterizes a eukaryotic cell whereas the absence of such characterizes a prokaryotic cell. • In a eukaryotic cell, the organelles bound by a double lipid bilayer include the nucleus, endoplasmic reticulum, Golgi apparatus, mitochondria, and plastids. • Also included are the plasma membrane and the cell wall. Some references consider single-membraned cytoplasmic structures as organelles, such as lysosomes, endosomes, and vacuoles. • Other less-strict characterization of an organelle includes the non-membrane-bound cytoplasmic structures, such as the nucleolus and ribosomes. Hence the correct answer is Option 2.