What term describes the hypothetical invisible form of matter that accounts for about 85% of matter in the universe?

• A. Dark energy
• B. Dark matter
• C. Neutrinos
• D. Antimatter

Answer: (B)

Dark matter is the invisible form of matter that makes up about 85% of the matter in the universe. It’s called dark because it doesn’t emit, absorb, or reflect light in any detectable way, yet it interacts through gravity. We infer its presence because stars on the outskirts of galaxies move faster than the visible mass should allow, and gravitational lensing and the way large-scale structures form can only be explained if there’s a lot of unseen mass present. In short, dark matter provides the extra gravity needed to hold galaxies together and shape the cosmos.

Other options don’t fit the same role. Dark energy is linked to the accelerated expansion of the universe, not to the mass content we experience as gravity in galaxies. Neutrinos are real particles with mass, but their total mass is too small to account for the majority of matter. Antimatter is just matter with opposite charge and would behave like ordinary matter if produced in large quantities; it would still interact electromagnetically if present in bulk, so it wouldn’t be the hidden mass responsible for the gravitational effects we observe.