(;SZ[19]AB[sr]AB[rr]AB[rq]AB[rp]AB[ro]AB[sn]AB[rm]AB[ql]AB[pl]AB[ol]AB[nl]AB[pk]AB[pj]AB[oj]AB[oi]AB[oh]AB[qj]AB[rj]AB[sj]AW[rs]AW[qs]AW[qr]AW[qq]AW[qp]AW[qo]AW[rn]AW[qn]AW[qm]AW[pm]AW[om]AW[nm]AW[ph]AW[pi]AW[qi]AW[ri]AW[si]AW[qk]AW[so]LB[so:a]C[Following on from the previous problem white has just played the marked stone 'a' at T5. This time black has plenty of large ko-threats. How to defend?]FF[4]GM[1]AP[Jago:Version 4.18] (;B[sp];W[rl] (;B[sl];W[sm]C[Ko for the life of the lower stones RIGHT]) (;B[sm];W[sl]C[Ouch! All gone.]) (;B[rk];W[sm])) (;B[sl];W[sp] (;B[sq];W[so] (;B[sp];W[ss]C[Black can't connect]) (;B[sm];W[ss];B[sp];W[so]C[oops!])) (;B[sm];W[ss];B[sq];W[so]C[Black loses the lower stones];B[sp]) (;B[sm];W[ss];B[sq];W[so];B[sp];W[so]C[oops!])) (;B[rl];W[sm]C[bye bye stones]) (;B[sm];W[rl];B[sp];W[sl]C[lower stones dead]))