Phosphine is prepared from which of the following methods?

By reacting calcium phosphide with water or dilute HCl

Phosphine (PH3) is typically prepared from the reaction of metal phosphides with water or dilute hydrochloric acid. Therefore, the correct method is:
1. By reacting calcium phosphide with water or dilute HCl

The chemical equation for this reaction is:

\[ \text{Ca}_3\text{P}_2 + 6\text{H}_2\text{O} \rightarrow 2\text{PH}_3 + 3\text{Ca}(\text{OH})_2 \]

This method involves the reaction of calcium phosphide (Ca3P2) with water to produce phosphine gas and calcium hydroxide.