阅读下面的短文，然后根据汉语或英语首字母提示写出所缺英语单词的正确形式。
    I had a very unusual experience on____ （星期天）。At around ten   o’clock in the morning, I was walking down the street when a UFO landed in f ____ of me. You can imagine how____ （奇怪的）it was! An alien got out and walked down the Center Street. I ____ （跟随）it to see where it was going, and I was very surprised when it went into a souvenir shop. While it was looking at the souvenirs, the assistant called the p____.