Dissertations / ERP, Application Software - suggestions on the topic for phd in software engineering [2]

hi friends, im trying to get enrolled into a phd programme in the field of S.E.,but i have a fewtopics in my mind which create a great confusion for me....as in which one would be the best for research....topics r:ERP,

Application Software,
MultiTasking,
Beta testing or
SDLC.plllllssssss help.