Final answer:
The binary compound from the provided options is b) LiBr, which is lithium bromide, consisting of lithium and bromine.
Step-by-step explanation:
The binary compound from the options provided is b) LiBr, which stands for lithium bromide. A binary compound consists of exactly two different elements. The option b) LiBr fits this definition as it is composed of lithium (Li) and bromine (Br) in a 1:1 ratio, thus making it a binary compound.
Other options, such as O₂, which is a pure element (oxygen), and Na₂SO₄ (sodium sulfate) and HCN (hydrogen cyanide), which are composed of more than two types of elements, do not qualify as binary compounds.