If white receives 1,black lays on the 4, A is the weakness of the green with.
White 1 is how to do what black wants to give up part of the X shall be attempting to select.
If at a later time may not be as the black 2 will be.
White 1 is light.
Black will easily connect each other if white got 1.
White 1 means,
It will be connected, but white 2 is bad.
White 1, so black is in danger.
If white has inadvertently 2 receives 3.
White defends A, black should simply connect because next black B is released after death.
Therefore, white 1 is the underbelly.