She found her calculator _______ she lost it.
A notice was placed by the river bank warning people to ___________ the thin ice.
I was close to being killed the other day. A car passed me at ____ I thought was a dangerous speed.
After half a year’s training, they were made entirely used ____ underwater.
Thank you very much for the trouble you have taken _________ me with my English.
Before the conference, a new problem came up __________ could speak on behalf of our group.