Choose the Statement That Is $\textbf{ true: }$

Multiple Choice

Choose the statement that is $\textbf{ true: }$

A) Outer electrons efficiently shield one another from nuclear charge
B) Core electrons effectively shield outer electrons from nuclear charge
C) Valence electrons are most difficult of all electrons to remove
D) Core electrons have the lowest ionization energies of all electrons
E) Two of the above are true.