Aluminium metal is frequently used as a reducing agent for the extraction of metals such as Chromium, Manganese etc. Explain why?

The free energy change for the formation of oxide of aluminium is highly negative ( -1000 to -1100) so , it can easily reduce any metal oxide abve it easily in ellingham diamgram as it lies bottom of the ellingham diagram.

give me answer for this question.

Aluminium is an highly electropositive metal like carbon. So these electopositive metals liberate a lot of energy in such reactions which helps to reguce other less electropositive metals...

That is why aluminium is also used to start thermite reaction

it is 3rd most abundant element and is cheap