valence electrons are the number of electrons in the outermost shell.
electron configuration is where the electrons are arranged in ascending order of energy shells
the electron configurations for the elements given are as follows
C - 2,4
Al - 2,8,3
Na - 2,8,1
Ca - 2,8,8,2
from the given elements, Aluminium has 3 electrons in its outermost shell.
answer is Aluminium
