The third answer because there are two of each atom
We have that the work function of the metal

From the Question we are told that
UV radiation (λ = 162 nm)
Kinetic energy 
Generally the equation for Kinetic energy is mathematically given as


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there are 2 copper atoms on the left side of the arrow, but none on the other side. there are also 7 oxygen atoms on the left hand side, but only 5 on the right hand side of the arrow.
-number of electrons
-atom size
-charge of the atom
-number of protons
name= calcium
atomic mass= 40.078 atomic mass unit
no of protons= 20
no of electrons=20