If the Cosmological Constant Exists, What Physical Effect Is Believed

Multiple Choice

If the cosmological constant exists, what physical effect is believed to create it?

A) New matter is constantly being created in the expanding voids between superclusters of galaxies, and the energy released by this creation accelerates the expansion of the universe.
B) No one knows. The cosmological constant has been hypothesized to exist because astronomers see the universal expansion accelerating, but its source is still a mystery.
C) Energy released by nuclear reactions in stars and then emitted into space is heating the universe and accelerating its expansion.
D) Virtual particles that constantly appear and disappear add energy to empty space, and this vacuum energy provides a constant repulsive force that accelerates the universe.