The Grand Tack Model Helps to Explain All of These

Multiple Choice

The Grand Tack model helps to explain all of these except one. Which is the exception?

A) Mars has a relatively small mass.
B) The asteroid belt contains a few icy objects as well as many rocky objects.
C) Neptune's current location would not allow it to grow rapidly enough to account for its large size.
D) The orbital motions of all the planets are in the same direction around the Sun.