. Which of the following best describes dark matter? (1 point) It's an area that has become too concentrated with stars.
O These are large clumps of galaxies.
O It is very large and invisible,
O Dark matter can only be detected using light beams.

Trumpeter a holds a b-flat note on the trumpet for a long time. person c is running towards the trumpeter at a constant velocity. person b is running away from the trumpeter at the same rate. person d is standing still the whole time. which person hears a frequency that is lower than the b-flat?

Plss anybody know how to do this? ? i need the answers from a through d

The passing of heat through a material while the material itself stays in place. a. radiation b. conduction c. convection