It's ten years since I didn't see him and he has changed beyond

It's ten years since I didn't see him and he has changed beyond recognition.
【正确答案】：didn't see改成saw。
【题目解析】：句意：距离上次见他已经十年了，他已经变得完全认不出来了。上次见他用一般过去时，所以应该用saw。