(;C[How many ko threats can you squeeze out of this living group? Side note: The ko is worth less than this group.]AB[ka][jb][jc][kc][lc][ld][md][nd][od][pd][qd][qc][rb][qa]AW[kb][lb][ma][mc][nc][oc][pc][pb][qb][nb]LB[jf:0][lf:1][nf:2][pf:3][rf:4]AP[goproblems]
(;B[rf]AW[pf][nf][lf];W[jf]C[Prove it!]
(;B[oa];W[pa]
(;B[na];W[ob]
(;B[ja];W[la];B[na];W[oa]C[You got 'emRIGHT])
(;B[na];W[oa];B[ja];W[la]C[You got 'emRIGHT]))
(;B[ja];W[la];B[na];W[ob];B[na];W[oa]C[You got 'emRIGHT])
(;B[ob];W[la]C[Only 2 Threats]))
(;B[ja];W[oa]C[Only 1 threat])
(;B[pa];W[oa]C[Only 1 Threat])
(;B[ob]C[Not Threat])
(;B[na]C[Not Threat]))
(;B[pf]PL[W]AB[oa]CR[oa]C[You are White now! Black just played the 1st ko threat. What would you do?];W[pa];B[ja]C[And that's 2...];W[la];B[na]C[3...];W[ob];B[na]C[4 at last!])
(;B[nf]PL[W]AB[oa]CR[oa]C[You are White now! Black just played the 1st ko threat. What would you do?];W[pa];B[ja]C[And that's 2...];W[la];B[na]C[And 3!])
(;B[lf]PL[W]AB[oa]CR[oa]C[You are White now! Black just played the 1st ko threat. What would you do?];W[pa];B[ja]C[And that's 2!])
(;B[jf]AB[oa]CR[oa]C[You chose 0 ko threats, but if Black plays the marked move White must answer or die - so that is clearly a ko threat.]))