The last time we had great fun was _____we were visiting the Water Park.
The moment ______Leo will never forget is ______he joined the Air Force
I prefer to work here because salaries are higher here than ______in my country.
The girl ___on the ground ___to me that she had ____the book on the shelf.
______himself to his research on the IT technology, he soon made a breakthrough.
_____the cause of the oil leaks, the specialists can not draw a conclusion before completing a thorough and detailed investigation.