:
This move is sente against Black's group in the top right, so White will get two moves in a row, locally.
:
White captures some of Black's stones.
:
As shown in the F-path ( 442), Black cannot win the resulting ko, should he try to connect all his stones along the edge. However, just living with his partial group on the upper edge is also not sufficient to win. White is comfortably ahead, as she has saved her group on the left side, and has also captured some of Black's stones in the upper left.