Tsumego (Capture) #5309417 (1-move)
Black to play — capture the marked white stones
Capture these stones
Why this move works
The answer is G2. The white stone in the corner (G1) is blocked at F1, leaving G2 as its only liberty.
Filling G2 removes its last liberty and captures it. Stones on the edge and in the corner have fewer liberties and are easier to capture.