Scientists photographed for the first time ever _____ wild gorillas used a stick to test the depth of a pool before getting into it, according to a recent study.
I still remember the days___ I spent ______ with you in Beijing.
In the face of _____ failure, it is vital that we should keep up _____ good state of mind.
______ the Venice Film Festival, we are to include high-quality films, ______ who makes them.
______ it rain tomorrow, we would have to put off the sports meeting.
By the time I saw the angry expression on his face, I ______ exactly what I was having to face. But not for a moment ______ I should quit.