Einstein Chose His Cosmological Constant to Be Positive

Einstein chose his cosmological constant to be positive.Why did he make this choice?

A) The choice was arbitrary because he did not realize at the time that it had physical implications.
B) If he had chosen a negative constant, his solutions would have been imaginary rather than real.
C) Unlike Newton, Einstein did not believe in an infinite universe, and the positive constant was needed to make his solutions describe a finite universe.
D) The positive constant implies a positive force that was needed to counter the negative force (implying an inward force) that resulted without the constant.