Which of the Following Statements Is True

Which of the following statements is true?

A) The krypton 1s orbital is smaller than the helium 1s orbital because krypton's p and d orbitals crowd the s orbitals.
B) The krypton 1s orbital is larger than the helium 1s orbital because krypton contains more electrons.
C) The krypton 1s orbital is smaller than the helium 1s orbital because krypton's nuclear charge draws the electrons closer.
D) The krypton 1s orbital and helium 1s orbital are the same size because both s orbitals can only have two electrons.
E) The krypton 1s orbital is larger than the helium 1s orbital because krypton's ionization energy is lower so it's easier to remove electrons.