If unrelated languages independently developed similar categories of physical objects, this suggests that these categories are less likely to be arbitrary choices, and more likely to reflect something essentially true about these objects. Therefore, (A) strengthens the argument that language has an essential correspondence to the things it describes.

(B) doesn’t strengthen the argument, because it’s consistent with language being based on agreed-upon conventions. If the second language evolved from the first, the conventions of the second language could have originated in the first one. (B) doesn’t suggest that two distinct groups independently came up with similar ways to describe the physical world. (Contrast with (A), in which the similar languages are independent.)

It makes sense that speakers of the same language would categorize physical objects in the same way. The fact that speakers of the same language use the same conventions doesn’t strengthen the argument that language has an essential correspondence to the things it describes.

(D) talks about sentence structures, while the essentialists’ argument is about the relationship between language and physical reality. Also, (D) is about languages that have something in common: they all came from scientifically sophisticated societies. It could be this shared trait that produced the similarities in language, not the fact that there is a concrete connection between language and the physical world.

It makes sense for people to think that their language accurately describes the world. It doesn’t matter if people believe that their personal language corresponds to natural categories of objects; the essentialists argue that language actually corresponds to the physical world.