There were ten green bottles hanging on a wall
Q Why would anyone hang ten bottles on a wall?
Q Of what relevance is their colour?
And if one green bottle should accidentally fall
G Is the word green really necessary? It has already been established that all ten bottles are green
Q Is the word 'accidentally' appropriate? Bottles do not in general purposely hurl themselves to the ground. Furthermore it is extremely fishy that the other nine bottles went on to suffer similar 'accidents'
They'red be nine green bottles hanging on he wall
Is this line not totally superfluous? The remaining quantity is obvious their colour has been established and will be ad nauseum throughout the remaining nine verses (to which the above comments also apply}