Mastering Astronomy Chapter 7 Concept Quiz?

Hey guys I'm not sure whether or not this is against the rules, but I'm looking for the answers to this quiz and don't seem to see them anywhere on this site. I went home for the weekend (stupid excuse, but it's true) and left my Astronomy book at school. So I was wondering if anyone had the answers to this one. I'll post the first two questions anyway because that would be a great help.

Thanks in advance!

Part A
The cores of the terrestrial worlds are made mostly of metal because ______.

    metals sunk to the centers a long time ago when the interiors were molten throughout
    over billions of years, convection gradually brought dense metals downward to the core
    the core contained lots of radioactive elements that decayed into metals
    the terrestrial worlds as a whole are made mostly of metal



Part B
Which internal heat source still generates heat within the terrestrial worlds today?

    Heat from convection.
    Heat from radioactive decay.
    Heat from differentiation
    Heat of accretion.