Answer: Drop out
Explanation: Drop out is the situation that is defined as abandoning a study in between after taking up or participating in it.This is considered as the act of withdrawal which can happen due to personal reason, lost interest in the course/study,etc.
Other options are incorrect because abandonment is leaving something before taking up or during the course, margin of error is used for defining the error that occurs in the sample survey and mortality signifies temporality or death.Thus, the correct option is drop out.
