Beginner Exercise 212 / Solution

Proof 1  

does not work, since almost fills with a bulky five and Black is dead. at a does not work for the same reason.

Proof 2  

throw-in fails too. Black can't play at a for shortage of liberties. He could make life in this way if he had one or more outside liberty.

Play elsewhere!  

Of course, White should play elsewhere (tenuki). We can observe three classes of possible blunders here:

• a doesn't change the status - it's nearly a move wasted, though it reduces Black's ko threats.
• b makes seki, losing about 30 points of territory.
• c is the worst, allowing Black to make life with Black a.