Which pair of elements belong to the same groups in the periodic table?

The elements in the question are as follows based on the periodic table: A=9 (Fluorine or F), B=11 (Sodium or Na), C=17 (Chlorine or Cl), D=12 (Magnesium or Mg), and E=13 (Aluminum or Al).

The modern periodic table is arranged in order of increasing atomic number, or the number of protons in the nucleus of an atom, which defines the element. There is a periodic repetition of the chemical elements as their mass increases, so from the way the table is arranged with similar elements in the same column or group, we can see that A (9, or F) lines up directly above C (17, or Cl), giving us answer C (A&C).