The correct answer is: Only I is implicit.
The statement “Delink degrees with jobs. Then, boys will think twice before joining colleges” implies that boys join college education for getting jobs. This is because if degrees are not required for jobs, then boys will have less incentive to go to college.
The statement does not imply that a degree is of no use for getting a job. It is possible that a degree is still useful for getting a job, even if it is not required.
The statement also does not imply that girls do not try for jobs. It is possible that girls try for jobs just as much as boys, even if degrees are not required for jobs.
Therefore, only assumption I is implicit in the statement.