Explain which alkaline earth metal is most likely to undergo hydrolysis.

It depends on your definition of hydrolysis - it usually means the
splitting of a large molecule into two smaller molecules upon the
addition of water. It's impossible to split the atom of an alkaline
earth metal (using water).

"Hydrolysis" can also refer to the splitting of a water molecule -- as
in electrohydrolysis.  The question would benefit from careful
restatement in any case.

The heaviest earthalkali metals are those that are hydrolyzed easiest;
so the answer would be Barium (Radium).

http://www.webelements.com/webelements/elements/text/Ba/key.html

:) Arsenic