Determine the number of protons and identify the correct symbol for an atom with 20 neutrons and 20 electrons.
A. 40 protons, 40/20 Ca
B. 20 protons, 20/20 Ca
C. 40 protons, 18/36 Ar
D. 20 protons, 20/40 Ca
E. 20 protons, 40/20 Ca