Why Won't Pluto Collide with Neptune

Multiple Choice

Why won't Pluto collide with Neptune?

A) Pluto orbits the Sun exactly two times for every three Neptune orbits, which ensures they never come close together.
B) Pluto is always much farther from the Sun than Neptune.
C) Actually, a collision of the two is inevitable within the next billion years.
D) Pluto's orbit never comes anywhere close to Neptune's orbit.