$($a$)$ The specific heat units $k\frac{J}{k}g*C$ and $k\frac{J}{k}g*K$ are identical and can be used interchangeably.

$($b$)$ The moving boundary work during a constant pressure process is $W_b=P_1{V}_{1}ln(\frac{V_2}{V_1}).$

$($c$)$ The specific heat at constant pressure is a measure of the variation of enthalpy of a substance with temperature.

$($d$)$ The energy content of control volume during a steady$-$state process is constant.

$($e$)$ For an ideal gas, the temperature increases during a throttling process.

$($f$)$ A rigid tank contains a fixed mass of air at $20C.$ If the temperature is increased to $40C,$ the pressure will double according to $PV=mRT.$