The rate of recombination of holes would increase due to increase in the number of electrons. Therefore, the number of holes would get reduced further........

plzzzzzz explain more briefly

It means since in n-type semiconductor number of electrons are greater than number of holes so when we form a semiconductor device by forming a Pn-junction diode then there would be more number of available electrons ready to combine with the holes through the junction as a result more combinations take place through the junction and the concentration of the holes will further reduce.