552. Its origin is still a mystery now． 它的起源至今仍是个谜。

551. I"d like to look at some sweaters． 我想看看毛衣。

550. I would rather stay at home alone． 我宁愿独自呆在家。

549. I think you have the Wrong number． 我想你打错号码了。

548. I really need to lose some weight． 我真的需要减肥了。

547. I expect to be there this evening． 我打算今天晚上到那儿去。

546. His boss might get angry with him． 他的老板也许会生他的气。

545. Here we are．Row M, seats l and 3． 哦，到了。M排，l号和3号。

544. Her handbag goes with her clothes. 她的手袋和她的衣服很搭配。

543. He suddenly appeared in the party． 他突然在晚会上出现了。