Question

Which best distinguishes between the inner and outer planets?
An asteroid belt is the dividing line between the inner and outer planets.
The increase in the number of moons divides the inner and outer planets.
The inner planets have cooler temperatures than the outer planets.
An additional planet found outside the main orbit is the dividing line.

Answer 1

either a or b 
not exactly sure which

Answer 2

An asteroid belt is the dividing line between the inner and outer planets . So the answer is A .