For White, is best.
forms a bent four and lives, and White can play at a to capture the stones at the corner.
and
is probably the strongest attempt to kill. The main thing to see in this problem is the tesuji at
, which makes
and
miai for life.
is wrong. White makes a placement at
, followed by an atari at
on the entire Black group which forces
to capture, finally a throw-in at
which makes the eye at the corner a false eye.