young phonetic professionals

One of the questions in my latest in-class test was: "What does a shaded cell in the table of pulmonic consonants indicate?" Here are two elucidating answers:

1. "The shading signals that this sound can't be produced by humans." (Your pet should give it a try.)
2. "It means that the articulation is judged to be impossible. Some of the cells are shaded because we don't speak them." (How true!)

The second group of students were given this question: "What does an empty cell in the table of pulmonic consonants indicate?"

1. "An empty cell means that it is not possible to produce. Such sounds physiologically in any language. "(Huh?)
2. "The shaded cells signify that its [sic] impossible to pronounce/voice it, whereas the white gaps show that it is possible to show, but there hasn't been found a way yet. (Maybe it was not found yet.)" (Oh my - those gaps!)
3. "The empty cells signals [sic] phonemes (sounds) which are physically impossible to produce or phonemes which are not found yet." (Track - Rover!)
4. "There are some empty cells because not every sound can be produced in every place and every manner. Apart from that there are more sounds in general but they do not exist in every language."

I'm depressed, desperate, hopeless, on the verge of insanity. Om! ॐ