What property did washoe’s language seem to have when she used an expression such as ""water bird"" to refer to a swan?

Productivity.

Explanation:

Productivity is a property of human language that enables humans to combine words or symbols , sounds or phrases in new ways in order to express particular ideas. It allows users to create new expressions, be creative or in other words open-endedness. Humans continually create new expressions and utterances by manipulating their linguistic resources to describe new objects and situations.

Washoe, a female 19 chimpanzee was the first non-human to communicate using American Sign Language (ASL) as part of a research experiment on animal language acquisition. By her use of expression of "water bird" for a swan, she is using the productivity property of human language.

yes, it can be both.

i think that will have something to do with the mississippi river but google will know the full answer for sure