Choosing A

@Meredith, (A) is supported in lines 37-41, where Posner argues that literary criticism and legal interpretation have different aims, which is synonymous to different/ incompatible goals. (D) is unsupported by the passage because the author never mentions that the interpretation of law relies heavily on legal precedent and even if you know that it is true, it is not appropriate to bring in outside knowledge on the LSAT.

Yep Meredith we are on the same page again I did the same thing

D doesn't work because it wouldn't impact its ability to be useful. D can be tempting because we'd assume that literary critics don't have a huge wealth of knowledge regarding legal precedent. However, the key word here is that we're assuming. We're never given any info about this in the passage, and we're looking for the primary difficulty according to Posner, so we can get rid of D. With A, in paragraph three, Posner says that literary criticism in general is about exploring the variety of meaning in texts, whereas legal interpretation is all about a single meaning. This would mean that their goals are fundamentally compatible with each other, so that's why A is correct.