Would you use this if you are playing with snow or something like that? I can't find the sense of this sentence
Why does the article "a" important? What is the clue whethet or not to use articled?
Because "Make big ball quickly" is not grammatical English. The article could also be "the" though
Because its not plural. Otherwise since it would add 들, unless its talking about a general subject, which i dont think it is for this case.