Please find the best result for White!
(japanese rules)
(;GM[1]FF[4]CA[UTF-8]AP[CGoban:2]ST[2]
RU[Japanese]SZ[4]KM[0.00]
PW[Weiß]PB[Schwarz]AW[cc][dd]AB[db][bc][ad][bd]C[White to play - what's the best he can do?]PL[W]
(;W[bb]CR[bb]
(;B[cb]CR[cb]
(;W[ca]CR[ca]
;B[ab]CR[ab]
;W[ba]CR[ba]C[Seki & Jigo! Four groups on a 4x4 board.... B A3 was necessary, if White can play there, Black will have to sacrifice a stone, giving White a win. RIGHT])
(;W[ab]CR[ab]
;B[dc]CR[dc]C[W A3 is too slow]))
(;B[dc]CR[dc]
;W[cb]CR[cb]
;B[cd]CR[cd]
;W[ab]CR[ab]C[White wins]))
(;W[cb]CR[cb]
(;B[bb]CR[bb]
(;W[ba]CR[ba]
;B[cd]CR[cd]
;W[ca]CR[ca]
;B[dc]CR[dc]
;W[ab]CR[ab]C[Seki, Black wins by one point (the prisoner)])
(;W[ca]CR[ca]
;B[ba]CR[ba]
;W[ab]CR[ab]
;B[cd]CR[cd]C[Black wins big]))
(;B[cd]CR[cd]
;W[bb]CR[bb]
;B[dc]CR[dc]
;W[ab]CR[ab]C[White wins, but B C1 was a mistake! This move should have been at B3.])))