Which New Idea Has Been Added into Our Theory of Solar

Which new idea has been added into our theory of solar system formation as a result of the discoveries of extrasolar planets?

A) Planets can migrate from the orbits in which they are born.
B) In addition to the categories of terrestrial and jovian, there must be an "in-between" category of planet that has the mass of a jovian planet but the composition of a terrestrial planet.
C) In some star systems, it is possible for jovian planets to form in the inner solar system and terrestrial planets to form in the outer solar system.
D) Some of the "exceptions to the rules" in our own solar system are likely to have been the result of giant impacts.