Tsumego From Games 6
In the 2002 Belgian Championships, I was leading against Mr. Wong. Although the black group in this diagram was surrounded on a large scale, White could only make an L group: White a to Black f keep White to one eye. Black has enough liberties to capture the L-group.
The correct answer is simply to extend as in the next diagram. Any beginner tsumego book will tell you that. But applying tsumego in games is another thing.