What is the combined gas law formula?

The law that combines Charles's law, Gay-law, Lussac's and Boyle's law is known as the combined gas law. It combines the three previously identified laws. These rules establish relationships between thermodynamic variables while keeping all other factors constant. In accordance with the combined gas law, which stipulates that the system's ratio of the product of pressure-volume and temperature remains constant, these variables are interdependent.

It is a combination of  three  known laws: Boyle's law PV = K, Charles' law $V / T = K$, and Gay-Lussac's law $P / T = K.$ Therefore, the formula for Boyle's law is: $PV / T = K$, 
where P = pressure, T = temperature, V = volume, K is constant.

Hence, option A is correct.