<u>Answer:</u> The correct option is B. elements.
<u>Explanation:</u>
A chemical compound is defined as the specie which is formed by the combination of two or more elements. For example: Water, carbon dioxide, etc..
Elements is defined as the chemical specie which consists of only one type of atom. For example: Hydrogen, Oxygen, etc..
Now, when hydrogen element and bromine element combines, it leads to the formation of a heteronuclear chemical compound known as hydrogen bromide having chemical formula HBr.
Hence, the correct option is B. elements.