----Who’s the man sitting under the tree? ----I don't ___ this man, but I’ve ___ him.

In the 21st century, all nations must take their ________of responsibility for the global safety.

I ___ the French written papers but failed in the English oral examination. 

——Watch! ——I ____ but ____ I ____ anything unusual.

When he was doing the software development project, he ___________ many problems that he had to solve on his own.