I'd say A: tidal waves. B, C, and D don't really seem to fit for me.
I believe the appropriate answer is a cooling-off period. The cooling off period us described as the state of returning to the offender's usual way of life between homicides. The key distinction between the serial killers and mass or spree killers is this emotional cooling off period in which the killer blends back into his/her normal life.
A I think sorry if I’m wrong
A galaxy where mainly stars and planets form around one or more spiral arms. (usually more?)
