I like to study Yoda Norimoto´s games because his name is similar to the famous Star Wars character. This situation is adapted from one of his games - and mr. Yoda solved it correctly! :-)
(;AW[rp]AW[ro]AW[qo]AW[qn]AW[rm]AW[rl]AW[rk]AW[qk]AW[qj]AW[qi]AW[ri]AW[sj]AB[sn]AB[rq]AB[pp]AB[qp]AB[po]AB[pn]AB[pm]AB[qm]AW[sq]AB[oq]AB[nq]AB[mr]AB[ns]AW[pl]AW[om]AW[on]AW[oo]AW[np]AW[mp]AW[lq]AW[lr]AB[op]AW[kr]TR[sq]C[White just played the marked stone. What should black do in a common game? (Sente is not important)]AP[goproblems]
(;B[sr];W[rr]
(;B[sp];W[qq]
(;B[sq]C[Nice, you saved a lot of points in the corner :-)RIGHT]MA[rn]MA[qr])
(;B[qr];W[sq]C[Picnic ko for white.]))
(;B[qq];W[ss];B[qr];W[sp]))
(;B[rr];W[sr]C[Black could do much better.])
(;B[qr];W[rr];B[qq];W[sr])
(;B[sp];W[so];B[sr];W[rr];B[sp]C[This ko is picnic for white, black cannot win it in a common game.])
(;B[rn];W[rr];B[qq];W[sp]))