Final answer:
Option A: The oxidation number of hydrogen in a compound other than a hydride is +1, following the general rule for hydrogen's oxidation state when bonded to nonmetals, but varies to -1 when bonded to metals.
Step-by-step explanation:
The oxidation number of hydrogen when it is in a compound other than a hydride is +1. This is a general rule, with hydrogen typically having this oxidation number when it is combined with nonmetals.
However, there are exceptions to this rule, such as when hydrogen is bonded to metals in the form of hydride ions, where its oxidation number is -1. For instance, in water (H2O), each hydrogen atom has an oxidation number of +1, whereas the oxygen has an oxidation number of -2. Yet, in compounds like sodium hydride (NaH), hydrogen takes an oxidation number of -1. It is essential to remember these basic rules when determining oxidation states in various compounds.