过去进行时。

解题思路： 如下
解题过程：
It was elelven on the morning of last Sunday. A girl rode a bike to the park.At ten past eleven, she got to the river in the park. She parked her bike there and saw two people swimming in the lake. She kept seeing them swimming there .Five minutes later, a thief stolen her bike while she was seeing them swimming.At eleven twenty, when the girl got back ,she found that her bike was lost .She was very sad and then called the police.
最终答案：略