<span>In a single replacement reaction (or simple displacement) an element reacts with a compound and takes the place of another element in that compound. The reaction that shows a sigle replacement is the third one. Where H2SO4 and Mg turn into H2 + MgSO4. In this case Mg replaces H2</span>
<span>Among the given choices, the third option is the only one which illustrates single replacement.
(3)H2SO4 + Mg --> H2 + MgSO4
A single replacement is also termed as single-displacement reaction, a reaction by which an element in a compound, displaces another element.
It can be illustrated this way:
X + Y-Z → X-Z + Y</span>
