Einstein Suggested That the Regular Change (Advance) in the Perihelion

Einstein suggested that the regular change (advance) in the perihelion of the planet Mercury could be explained by:

A) the presence of a planet inside the orbit of Mercury, whose gravity influenced Mercury
B) a distortion in spacetime caused by the gravity of the Sun
C) the pull of a small black hole that orbits our Sun so closely that we are not able to see it
D) the presence of a strong magnetic field in the Sun, which causes huge outburst of material
E) a distortion in our view of the solar system caused by the Earth's atmosphere