The answer is GATCC. According to the complementary rule, guanine will bind cytosine (G-C) and vice versa (C-G) while adenine will bind thymine (A-T) and vice versa (T-A). Therefore, from the beginning of the sequence CTAGG, G will bind C, A will bind T, T will bind A, C will bind G, and C will bind G. The correct matching sequence for CTAGG is GATCC.