What are the answers to c. and d?

The answer to C. is densities

The answer to D. could be anythingtry "magnet" for the first blank and "metals" for the second blank

Because the earth is not round ,but it may seem round when viewed from ,our planet but true some points earth is not round was an oblate spheroid -a square that it squashed as globe however is not even a perfect oblate spheroid.in fact isaac newton's first proposed that earth was not perfectly round but it was an oblate spheroid instead.that mean a square that is squashed as its poles and swollen at the

Very hard to understand