(;AB[po]AB[pn]AB[pm]AB[pl]AB[pk]AW[qk]AW[qj]AW[qi]AW[pi]AW[qn]AW[ro]AW[qp]AW[pp]C[Black wants to reduce White's territory. Which of A, B, C, D is best?FORCE]LB[ql:A]LB[rl:B]LB[qm:C]LB[rm:D]AP[goproblems] (;B[rl];W[ql] (;B[rm];W[qm]C[:|]) (;B[qm];W[rm] (;B[sm];W[rn]C[White is safe. See the comment in the variation where Black plays S6 instead of T7.]) (;B[rn]MA[pm]MA[rn]MA[rl]C[Compare the table shape here to the correct solution. The last leg of the table, S6, doesn't work here.]MA[pl]))) (;B[rm];W[qm] (;B[rl];W[ql]C[:|]) (;B[ql];W[rl] (;B[qo];W[rn];B[rk];W[sm]) (;B[rn];W[rk];B[qo];W[rp]C[RIGHT]) (;B[rk];W[rn] (;B[sl];W[rj]C[Right. Observe the table shape in relation to the two Black stones that were originally facing the gap in White's wall.RIGHT]MA[pl]MA[pm]MA[rk]MA[rm]) (;B[sm];W[rj] (;B[sk];W[sj];B[sl];W[sn];B[rl];W[qo]C[Black can do better.]) (;B[sl];W[sj]C[RIGHT]))))) (;B[ql];W[rm];B[rl];W[rk]C[Black can do better.]) (;B[qm];W[rm];B[rl];W[ql];B[sm];W[rn]C[White is safe.]))