Why Has Mercury Become Locked into a 3-To-2 Spin Orbit

Why has Mercury become locked into a 3-to-2 spin orbit coupling instead of a 1-to-1 coupling like the Moon around Earth?

A) Mercury feels a stronger gravitational pull from the more massive Sun than the Moon does from Earth, so its rotation became locked on the Sun before it had slowed enough for a 1-to-1 lock.
B) Mercury's orbit is very eccentric, so its orbital speed varies while its rotation rate remains constant, preventing a 1-to-1 lock.
C) Mercury's rotation rate is still slowing down, and the apparent 3-to-2 lock is actually just coincidence.
D) Mercury's orbit is highly inclined (tipped up at an angle to the orbits of the other planets) , so the Sun sometimes pulls more on Mercury's north pole and sometimes more on its south pole.