Draw a structure showing how a G hydrogen bonds with a C.

Answer:
             Three hydrogen bonds are formed between Guanine (G) and Cytosine (C).

Explanation:
                    Hydrogen bond takes place when the hydrogen atom directly bonded to most electronegative atom (F, O or N) of one molecule interacts with the most electronegative element of neighbor molecule. The hydrogen atom in this case attains a partial positive charge and it interacts with a element with partial negative charge of neighbor molecule.
                    Following figure show the three hydrogen bonds (green dashed lines) formed between Guanine (Red) and Cytosine (Blue).