Which type of radioactive decay occurs in the following reaction?

Beta emission

Explanation:

Since in beta emission (-1e^0) atomic number increases by one unit without changing the mass number.

Here mass number increased from 53 to 54 by the emission of beta particle.

the mantle

explanation:

earth is divided into three layers: the crust or the outermost layer on which we live; the underlying, middle layer - the mantle - and the core (the innermost layer of earth).