The molar specific heat of a gas as given from the kinetic theory is 52R. If it is not specified whether it is C_p or C_V, one could conclude that the molecules of the gas.

Correct option is D. Can be mono atomic or rigid diatomic
Given that
The molar specific heat of a gas as given from the kinetic theory is 52R
As we know that
Cv = fR/2
and
Cp = (1 + f/2)R
where f is the degree of freedom and R is gas constant
Case 1:
If the given specific heat is Cv, then
f = 5
then the gas will rigid diatomic
Case 2:
If the given specific heat is Cp, then
f = 3
Then the gas will be monoatomic