(;
AB[nc][qc][od][pd][pj]
AW[rc][qd][pe][pg]
C[Black's response to the marked play?

Source:
    American Go Journal, Vol. 35, No. 2, p. 37
    Originally from Go Review X, May 1970.]
TR[rc]
(;
B[qb]
C[Based on last week's problem, you should realize that passively defending with this descent gives White a gift.];
W[re]
C[White is happy to defend here, which creates lots of eye-space.]
)
    (;
    B[qe]
    C[Cutting here looks promising, but Black needs to look a couple moves ahead.];
    W[rd];B[pf];W[qf]
    C[Black needs to know about this tesuji, that sometimes goes by the name "ko lock".  Now White can connect underneath.];
    B[oe]
    C[But this result is still better for Black than the previous variation.];
    W[re]
    C[For example ...];
    B[og]
    C[Black can confine White's group.]
    )
    (;
    B[rd]
    C[This simple cut is good for Black and limits White's potential.];
    W[qe];B[rb];W[pc]
    C[White has no other effective alternative but to play the following sequence.];
    B[qb];W[re];B[sc]
    C[For now Black has nothing to worry about, because the marked stone currently cannot cause trouble.]
    TR[pc]
    )
)

