Why Did Einstein Introduce His Cosmological Constant into the Original

Why did Einstein introduce his cosmological constant into the original field equations for general relativity?

A) The constant was necessary to make the solutions describe an expanding universe.
B) Experimental evidence at this time (before Hubble) suggested a static universe, and this constant was required to produce static solutions.
C) The constant represented the acceleration of gravity near Earth's surface, and it was necessary to make the nonrelativistic limit of the solutions compatible with Newton's results.
D) The constant represented the speed of light, and its inclusion was necessary to produce solutions that were compatible with the postulates of special relativity.