The correct option is B [ML5T−2]
Principle of homogeneity of dimensions and only like quantities can be added or subtracted from each other.
van der Waals' equation is
(p+aV2)(V−b)=RT
Here,
Dimensions of aV2= Dimensions of p,
Dimensions of a= Dimensions of [pV2]
=[ML−1T−2][L3]2
=[ML5T−2]