Why Did Einstein Introduce the Cosmological Constant into the Equations

Why did Einstein introduce the cosmological constant into the equations of his General Theory of Relativity when describing the universe?

A) Einstein did not realize that black holes would exist at the centers of galaxies and pull everything into them
B) Einstein's equations required the universe to expand or contract; he could not imagine or accept it doing either one, so he put a factor in to stop it from moving
C) Einstein talked to Hubble and learned about Hubble's observations of the expanding universe, which made him so uncomfortable that he decided to change his equations
D) Einstein had a hunch that the universe was accelerating (speeding up its expansion) back in 1918 and so introduced the constant into his equations to describe that
E) Einstein liked cups of tea in the afternoon, and his constant was a comment on that habit