根据句意和首字母，填写所缺单词。

1. He is a v_______, and he often treats some animals.

2. His father is able. He can s_______ this problem by himself.

3. His grandfather can't walk and has to sit in a w_______.

4. I love dogs because they never c_______ and they're grateful.

5. He is my best friend. We all t_______ in him.