Can I say , Yesterday was a rainy day . John fell down and hurt his knee . ( a ) John tried to walk but failed . Luckily , he saw two scouts was on the way to him .

Q with options: Give answer the following question using evidence from the above passage: Why may have John hurt his knee ?
Choices:
* The scouts pushed him .;
* He slipped on a wet surface .;
* He was pushed by the scouts .;
* He was fooling around .;
He slipped on a wet surface .