In a game, I made the mistake and my oponent miss this simple tsumego ^^
(;AB[ck]AB[dk]AB[ek]AB[fl]AB[gl]AB[gk]AB[gj]AB[hk]AB[il]AB[eh]AB[fh]AB[gh]AB[hh]AB[ih]AB[jh]AB[kh]AB[li]AB[mi]AB[kj]AB[kk]AB[lk]AB[mk]AW[ik]AW[jk]AW[jl]AW[kl]AW[ll]AW[ml]AW[jj]AW[ji]AW[ki]AW[hi]AW[hj]AW[gi]AW[fi]AW[fj]AW[ej]AW[cj]AW[dh]AW[dg]AW[eg]AW[fg]AW[bj]LB[eh:A]LB[dg:B]C[White answer B to A. Show him his eror]AW[fk]SZ[13]AP[goproblems]
(;B[dj];W[ii]LB[ij:1]LB[lm:2]C[Wrong! two eyes. And the C5 cut don't work.CHOICE])
(;B[ei];W[dj]C[And now ?]
(;B[ii];W[ij];B[di];W[ci];B[ch];W[bh]C[No, the shicho is bad for black.CHOICE])
(;B[ij];W[ii];B[di];W[ci];B[ch];W[bh]C[No, the shicho is bad for black.CHOICE])
(;B[di];W[ci]C[And Now ?]
(;B[ch];W[bh]C[No, the shicho is bad for black.CHOICE])
(;B[ii];W[ij];B[ch];W[bh]C[No, the shicho is bad for black.CHOICE])
(;B[ij];W[ii];B[ch];W[bh]C[No, the shicho is bad for black.CHOICE])))
(;B[di];W[dj];B[ei];W[ci]C[And Now ?]
(;B[ch];W[bh]C[No, the shicho is bad for black.CHOICE])
(;B[ii];W[ij])
(;B[ij];W[ii]))
(;B[ii];W[ij]
(;B[ei];W[dj];B[di];W[ci];B[ch];W[bh]C[No, the shicho is bad for black.CHOICE])
(;B[dj];W[di]
(;B[ei];W[jm]
(;B[lm];W[hl]
(;B[hm];W[im]
(;B[hl]C[Good white is dead !RIGHT])
(;B[el];W[hl]C[Consider white would win the ko];B[gm]C[Good! white is dead !RIGHT])
(;B[em];W[hl];B[gm]C[Good! white is dead !RIGHT])
(;B[fm];W[hl]
(;B[el];W[gm]C[wrong ko!CHOICE])
(;B[gm];W[el]C[Wrong you are deadCHOICE]))
(;B[gm];W[hl];B[el]C[Good! white is dead !RIGHT]))
(;B[el];W[hm]C[Wrong, white have two eyes.CHOICE]LB[im:1]LB[km:2])
(;B[em];W[hm]LB[im:1]LB[km:2]C[Wrong, white have two eyes.CHOICE])
(;B[fm];W[hm]LB[im:1]LB[km:2]C[Wrong, white have two eyes.CHOICE]))
(;B[im];W[lm]C[WrongCHOICE])
(;B[hm];W[lm]C[WrongCHOICE])
(;B[el];W[lm]C[WrongCHOICE]))
(;B[jm];W[ei]C[WrongCHOICE]))
(;B[di];W[dj]
(;B[ci];W[ei]C[White have too liberties, you can't kill him this wayCHOICE])
(;B[ei];W[ci];B[ch];W[bh]C[No, the shicho is bad for black.CHOICE])))
(;B[ij];W[ii]
(;B[dj];W[di])
(;B[ei];W[dj];B[di];W[ci];B[ch];W[bh]C[No, the shicho is bad for black.CHOICE])
(;B[di];W[dj]
(;B[ci];W[ei]C[Wrong, white ever have two eyesCHOICE])
(;B[ei];W[ci];B[ch];W[bh]C[No, the shicho is bad for black.CHOICE]))))