During Joule-Thomson expansion of gases

Answer: Option A

During, joule-thomson effect basically the change in internal (inter-molecular) energy and change in pressure energy will be equal to zero hence, enthalpy will remain constant.
$$\begin{array}{rl}& dU+d\left(PV\right)=0\\ & \Rightarrow d\left(U+PV\right)=0\\ & \Rightarrow d\left(H\right)=0\\ & \text{or }H=\text{constant}\text{.}\end{array}$$