阅读下面短文，根据短文内容用方框内所给词语的适当形式填空，使短文语义完整。（10分）

to，must，ask，unusual，it，when，early，who，notice，if

　　My name is Jim White. I live in America. I had a very  1 experience on Sunday. I saw a UFO in the daytime.   2 this spring, I went outside with my friend Bill  3 lived close to me. We were walking to a hill  4 I saw a large bright light dancing in the sky. I called Jim and asked him to look up. He kept  5 , “What is that?” “A UFO!” I shouted excitedly. I  6 it was round and red in the center.
　　After we looked at  7 for a moment, we found it seemed that it had wings, but it was still round. Bill would not believe me when I told him it  8 be a UFO. We shouted  9 it and we wished that it would land. We wanted to know  10 there was an alien in it. But soon it disappeared. I guessed we scared it off.
　　Do you believe me? It’s a true story.