Following the rule of base-pairing, cytosine (C) always pairs with guanine (G).
The base-pairing rule of nucleic acids was proposed by Chargaff.
According to Chargaff, Adenine bases always pair with Thymine bases (or Uracil) while Cytosine bases always pair with Guanine bases.
Thus, the only correct option is C pairing with G.
More on Chargaff's rule can be found here: https://brainly.com/question/6260514?referrer=searchResults