This came from a game which I later lost - the initial position was much more complicated in the game, and I lost track of the liberties (or lack thereof XD) of one of the groups involved. At any rate, B played the marked stone, thinking it would save his group. Show him he's wrong.
(;AP[goproblems]AB[fd]AB[gd]AB[gc]AW[fc]AW[ec]AW[ed]AB[eg]AB[fg]AB[gg]AW[df]AW[dg]AW[eh]AW[fh]AW[gh]AW[hf]AW[he]AW[hd]AW[hg]AW[ic]AB[hh]AB[ih]AB[ig]AB[if]AB[ie]AB[jd]AB[jc]AB[fe]TR[fg]TR[eg]TR[gg]C[w to respond to b's marked stone](;W[ff](;B[gf](;W[ge](;B[ef](;W[ee];B[ff](;W[gb]C[This is what happens if b doesn't read ahead at allRIGHT])(;W[hc];B[gb](;W[hb]C[RIGHT])(;W[ga]C[RIGHT])(;W[fb]C[RIGHT])(;W[ha]C[RIGHT])(;W[ib]C[RIGHT])(;W[jb]C[RIGHT])(;W[ia]C[RIGHT]))(;W[hb]C[RIGHT]))(;W[hc];B[ee]))(;B[hc];W[ef];B[ib];W[id];B[hb]C[best moves for both sidesRIGHT]))(;W[ef];B[ge])(;W[ee];B[ge]))(;B[ef];W[ee];B[gf];W[ge](;B[hc];W[ff];B[ib];W[id];B[hb]C[Best moves for both sides.RIGHT])(;B[ff](;W[gb];B[hc];W[hb]C[What happens if b doesn't read ahead at allRIGHT])(;W[hc];B[gb](;W[hb]C[RIGHT])(;W[ha]C[RIGHT])(;W[ib]C[RIGHT])(;W[ia]C[RIGHT])(;W[jb]C[RIGHT])(;W[ga]C[RIGHT])(;W[fb]C[RIGHT])))))(;W[gf];B[ff](;W[ib];B[hc];W[id];B[jb]C[Oh, no! g14 killed w.])(;W[hc];B[gb]C[4 vs 6 - g14 killed w!]))(;W[ef];B[ff](;W[ib];B[hc];W[id];B[jb]C[4 vs 5 - e14 killed w!])(;W[hc];B[gb]C[5 vs6 - e14 killed w!]))(;W[ee];B[ff])(;W[ge];B[ff]))