Here is an easy one for you! In the late endgame of a very close game, black played elsewhere in answer to the marked white stone. This wasn't his best idea! Do you know why?
(;SZ[19]AW[am]AW[bm]AW[cm]AW[em]AW[dn]AW[eo]AW[ep]AW[cq]AW[eq]AW[dr]AW[er]AW[ds]AB[an]AB[bn]AB[cn]AB[bo]AB[do]AB[ap]AB[dp]AB[bq]AB[dq]AB[cr]AB[cs]TR[am]C[White to move! What can he do?]GM[1]FF[4]CA[UTF-8]AP[CGoban:2]ST[2]RU[Japanese]KM[0.00]TM[]PW[Weiß]PB[Schwarz]PL[W]
(;W[cp]
(;B[co]
(;W[br];B[bp]
(;W[cq];B[cp]
(;W[bs];B[cq]
(;W[ar]TR[am]C[It's a seki, counting three points for black (the three captured stones). If he had answered the marked stone, there would have been ten points of territory - black lost seven points here! CHOICERIGHT])
(;W[aq];B[ar]))
(;W[ar];B[aq]))
(;W[bs];B[cq]
(;W[ar];B[aq])
(;W[aq];B[ar]))
(;W[ar];B[cq])
(;W[cp];B[cq]))
(;W[bs];B[br])
(;W[aq];B[ar])
(;W[ar];B[bp]
(;W[cq];B[br])
(;W[br];B[cq])))
(;B[br];W[co];B[bp]TR[co]C[This isn't blacks best try - he only has five points left compared to the six white earned, and it is gote also. Black should have played 2 at the marked point! RIGHT]))
(;W[br];B[cp]
(;W[bs];B[cq];W[ar];B[aq]C[This comes to nothing.])
(;W[ar];B[aq]))
(;W[co];B[cp])
(;W[bp];B[cp])
(;W[ar];B[br];W[cp];B[co])
(;W[bs];B[br];W[cp];B[co]))