Final answer:
The predominant element in melamine is nitrogen, as indicated by its molecular formula C3H6N6, which contains the highest number of nitrogen atoms. The correct option is C.
Step-by-step explanation:
The predominant element in melamine is nitrogen (N). Melamine is an organic compound with the formula C3H6N6.
If we break down the components of melamine based on the given options, we find that its molecular structure includes six nitrogen atoms, six carbon atoms, and six hydrogen atoms, which matches the elements listed in option d (oxygen, carbon, hydrogen, and nitrogen).
Among these, nitrogen is the most prominent element by number of atoms. Therefore, the answer to the question is nitrogen (c).