Beginner Exercise 229

L-group  

To recap, the Black group is known as the L-group, which is a basic dead shape. It is known that Black moves at a or b are sente, and having additional Black stones at c and d does not help Black to live.

Problem  

The problem for this beginner exercise is: how to answer the hane at ? You may assume that all outside stones are alive, as per usual conventions in life-and-death.

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