Adapted from a problem composed by Horace Cheshire (1911). All five black groups are unconditionally alive, even if black does nothing but pass for the rest of the game. One of the groups contains a stone more than necessary. Which one?
(;AB[rh]AB[sh]AB[li]AB[mi]AB[qi]AB[ri]AB[jj]AB[kj]AB[mj]AB[qj]AB[sj]AB[jk]AB[lk]AB[nk]AB[rk]AB[gl]AB[hl]AB[kl]AB[ml]AB[nl]AB[rl]AB[sl]AB[fm]AB[gm]AB[im]AB[km]AB[lm]AB[fn]AB[hn]AB[in]AB[qn]AB[rn]AB[go]AB[ho]AB[ko]AB[lo]AB[mo]AB[po]AB[ro]AB[so]AB[kp]AB[mp]AB[pp]AB[qp]AB[sp]AB[lq]AB[nq]AB[rq]AB[lr]AB[mr]AB[nr]AB[rr]AB[sr]LB[fl:A]LB[ki:B]LB[kq:C]LB[qk:D]LB[qq:E]C[Which of these groups contains an unnecessary stone? Choose one of A,B,C,D,E.FORCE]PL[W]GM[1]FF[3]
(;W[fl]C[])
(;W[ki])
(;W[kq])
(;W[qk])
(;W[qq]MA[so]C[Correct. This group would be unconditionally alive even without the marked stone.RIGHT]))