Question

Hydrogen acts as a reducing agent and thus resembles
A. Halogen
B. Noble gases
C. radioactive elements
D. alkali metals

Answer 1

When a substance is oxidised, it loses electrons in a chemical reaction. If a substance is reduced, it obtains electrons in a reaction. A redox reaction is defined as a reaction that involves both oxidation and reduction.

Complete answer:
Alkali metals have a $n{s^1}$ valence electronic arrangement. By eliminating one electron, they can achieve the noble gas electronic state, which is a stable configuration. They can quickly lose an electron due to their low ionisation potential and the minimal nuclear charge. As a result, alkali metals are thought to be a powerful reducing agent.
A reducing agent is a chemical that loses electrons to other compounds in a redox process and is oxidised to a higher valency state.
The reducing agent becomes oxidised after losing electrons, causing the opposing reactant to become reduced by giving electrons.
Alkali metals have a tendency to lose an outer shell electron, resulting in cations with a charge of
$+ 1$.
Hydrogen acts as a good reducing agent which means that when hydrogen gas is passed over hot metallic oxides of copper, lead, iron. It removes oxygen from them and thus reduces them to their corresponding metal.
Hydrogen acts as a reducing agent and thus resembles alkali metals which are good reducing agents.
Hence, the correct option is D. alkali metals.

Note:
Hydrogen gas acts as a reducing agent when it reacts with nonmetals and as an oxidizing agent when it reacts with metals. Alkali metals are the most electropositive elements, and they are not found in their pure condition for the same reason.