This must be true. As shown in the diagram, by chaining the conditional claims, we see that conceptual thought is a necessary condition for language.

This could be false. (B) says “Conceptual thought → Use of verbal signs for objects.” In our diagram, we only have conceptual thought as a necessary condition; we don’t know what conceptual thought is a sufficient condition for.

This could be false. We have no information about which topics are possible to think about conceptually.

This could be false. In our diagram, “human” is a necessary condition for “use of verbal signs for objects.” We are not given “humans” as a sufficient condition for anything, so we don’t know anything that “all humans” can do.

This could be false. We know that many animals can vocally express at least one feeling (hunger). It could be the case that vocal expression of hunger requires conceptual thought; our stimulus just doesn’t address this.