1.while,took,we,down,were,off,walking,the UFO,the street

1.We were walking down the street,while the UFO took off.
2.The girl was buying a souvenir when the police called the alien.
3.The girl saw the alien get out when she was shopping.
4.I had a very unusual experience last Sunday.
5.It was raining when the plane landed in the airport. 再答： 没关系，这类型题我觉得这样做： 第一步：找主语，能做主语的必须是名词或者是带有名词性质的词、结构或句子等，所以就要先把一排单词里带有名词性质的挑拣出来，看哪个作为主语更合适，更通顺。 第二步：找谓语动词，同上，把适合做谓语动词的选项挑出来，结合意思，想想看哪个做谓语合适。 第三步：根据主谓结构差不多就能估计出来整体句意，因为根据语法，主语和谓语这两个无非就那么有限的几个选择而已，所以你可以试着去想这句话大体是个什么意思。 第四步：选择排列好以后检查语法错误有没有，检查句意是否通顺。