TsumegoFromGames115/Solution

 

The lower left needs a move by black, otherwise it will die like this. (If captures at a instead, White still plays and black cannot prevent white from connecting under due to damezumari.)

 

The lower right is alive. White's strongest attack is this .

 

Alive...

 

Alive...

 

Strongest resistance. Note that if white had played the original ( in this diagram) at a, the black group would not have been able to live like this.