They seem to be using "что" for the russian question word, which serves the correct function in my experience. [1] However I'm not sure what the "a" interjectio

They seem to be using "что" for the russian question word, which serves the correct function in my experience. [1] However I'm not sure what the "a" interjection is supposed to be and I don't think I have heard it used in practice, although I'm not a native russian speaker. [1] http://journals.plos.org/plosone/article/figure/image?size=large&id=info:doi/10.1371/journal.pone.0078273.t001 http://journals.plos.org/plosone/article/figure/image?size=l...