I thought of this problem after taking a closer look at problem 12222. This is quite simple, but not to be overlooked!
(;AW[rb]AW[qb]AW[rc]AW[sc]AW[nb]AB[mc]AB[od]AB[pd]AB[qd]AB[qc]AB[rd]AB[nd]C[How should white defend against black 1? If you think white doesn't need to defend in order to live unconditionally in the corner, play T for tenuki.]LB[pf:T]AW[nc]AW[mb]AW[oc]AW[pb]AB[pc]AB[md]AB[lc]AB[lb]AB[la]AB[oa]LB[oa:1]AP[goproblems]
(;W[pf];B[ma]C[Ok then, please demonstrate how to live in the best way.]
(;W[ob];B[na]
(;W[sa];B[pa];W[qa]C[Good.RIGHT])
(;W[pa];B[ra];W[sa];B[sb]C[Ko.])
(;W[qa];B[sa]))
(;W[na];B[ob])
(;W[pa];B[ra]
(;W[sa];B[sb]C[];W[qa];B[na]C[You could've saved the four stones.])
(;W[na];B[ob])
(;W[ob];B[na];W[sa];B[sb]C[Ko.]))
(;W[qa];B[sa]
(;W[na];B[ob])
(;W[ob];B[na]))
(;W[sa];B[ob]C[You could've saved those four stones.])
(;W[ra];B[pa]
(;W[na];B[ob])
(;W[ob];B[na])))
(;W[ob]C[This is unnecessary.])
(;W[pa]C[This is unnecessary.])
(;W[qa]C[This is unnecessary.])
(;W[sa]C[This is unnecessary.])
(;W[na]C[This is unnecessary.])
(;W[ma];B[ob])
(;W[ra]C[This is unnecessary.]))