Hey!

See, as given in question no quantity is dimensionless, but ln(BD) is a dimension less quantity as natural log has no dimensions.

Which means [A] [D] =[C]

And after checking a the options, we can conclude that c option that is (A-C) /D is not a meaningful quantity as A and C has different dimensions, thus can't be subtracted from each other.

Hope it helped to clear your delimma.

Thank you