The placement at is the tesuji;
offers the strongest resistence. However,
and
are clever plays, because
cannot connect at
because of a shortage of liberties.
takes away the second eye.
Black tries to expand the eye space, but the hane at
destroys the possible eye at the corner. After
, black dies from a straight three.
The simplest way of making ko is to hane at .
Black lives.
In the main line, if extends into the corner, then
to
forces a seki.