Answer:
The two gases are
and
Step-by-step explanation:
According to Graham law of effusion for a binary mixture of gases-

Where
and
are rate of effusion of gas-1 and gas-2 respectively.
and
are molar mass of gas-1 and gas-2 respectively.
Gas Molar mass (g/mol)
32
71
CO 28
44
146
So, clearly molar mass of
is greater than molar mass of
. Hence
will effuse faster.
Also,

Hence, option (d) is correct.