What Precipitates Premature Closure

What precipitates premature closure?

A) the scientific community deprioritizes investigations of a topic for political or cultural reasons
B) the subjects of a panel study decline continued participations in the research,or are no longer suitable candidates for the research
C) the subjects of a case study decline continued participations in the research,or are no longer suitable candidates for the research
D) a researcher feels he or she has the answers and does not need to listen,seek information,or raise questions any longer
E) a researcher is forced to conclude an investigation due to financial,temporal,or other practical constraints on the research process