Context: 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 .

Question: Why may have John hurt his knee ?
Options:
0. The scouts pushed him .
1. He slipped on a wet surface .
2. He was pushed by the scouts .
3. He was fooling around .
Answer: 1