B. The element nitrogen is made up only of nitrogen atoms.
Step-by-step explanation:
Dalton stipulated , in his theory, that all the atoms of pure elements were identical. However different elements had different kinds of atoms that differ in their size and mass. The other stipulations of Dalton's theory were that atoms are the smallest unit of mass and were indivisible – this was later rebutted by advanced atomic theories .
Another major contribution by Dalton's theory is that chemical reactions involved the rearrangement of atoms observing the law of conservation of mass,