In an Exoplanet System in Which a Gas Giant Has

Multiple Choice

In an exoplanet system in which a gas giant has an orbit very close to its star, how commonly have astronomers found other planets at larger orbital distances from the star?

A) extremely rarely, because the migrating gas giant drives all the other planets into the star
B) extremely rarely, because the migrating gas giant ejects all the other planets from the system
C) extremely rarely, because the existence of a close-in gas giant implies that all the available material was accreted onto that planet
D) in about half of such exoplanet systems