我在清理书桌时偶然发现了这些照片。

I ___stumble ___across these photographs while I was cleaning out my desk.

经过数月的房产网站浏览和周末看房，我们终于偶然发现了拉文德路上这栋惊人的排屋末端。

After months of property website surfing and house-hunting over weekends, we finally ___stumble ___upon this amazing end of terrace house in Lavender Road.

在为我的论文研究时，我在图书馆档案中偶然发现了一份罕见的手稿。

While researching for my thesis, I ___stumble ___on a rare manuscript in the library archives.