A rigid container

Let us use the formula,

Heat supplied to a gas, dQ = nC_vdT.

Where,

n is the number of mole of the ags

C_v is the specific heat of the gas at constant volume T is the temperature

Putting the values in the above formula, we get

dQ = 3.0 cal = (3.0 x 4.2)J = 12.6 J.

dT = 1°C, n = 1.

Therefore, C_v is approximately equal to 12.6 J/mol/°C ~ 1.5R = 3R/2

We know,

Where C_p = specific heat at constant pressure

R = universal gas constant = 8.314 J/kg/mol

which holds for monoatomic gases.

Helium and Argon are monoatomic and so options (a) and (b) hold.