When We Say That Human Language Is "Conventional," We Mean

When we say that human language is "conventional," we mean that:

A) Humans are very conservative and rarely change their way of speaking.
B) The words in human languages have no inherent relationship to the things they stand for.
C) All languages follow the same grammatical rules or conventions.
D) Human language was invented at a convention.
E) All human languages have basically the same structure and differences among them are only superficial.