Question

Critical Reasoning -- Assumption Argument: 
"Flexible working hours will increase employee productivity because people perform best during the hours when they feel most energetic." 

Which of the following is a necessary assumption? 

1. Employees can accurately identify the hours when they are most productive. 
2. Productivity depends only on the time of day. 
3. Employees dislike rigid schedules.
4. Flexible hours reduce overall work time. 

Hint:

A necessary assumption is something that must be true for the argument to work. Try using the negation test: if negating the statement weakens the argument, it is a necessary assumption.

Answer 1

The argument only works if employees can actually tell when their own energy peaks are, since flexible hours are only useful for boosting output if people use that flexibility to work during their best hours. That is not something the argument states outright, it is something it quietly leans on, which is exactly what a necessary assumption is. The other choices either are not required for the conclusion to hold (whether employees dislike rigid schedules is irrelevant to whether output rises), overreach beyond what is needed (productivity depending only on time of day is far stronger than the argument requires), or run against the conclusion (cutting total work time undercuts the productivity claim rather than supporting it). So the piece the argument truly cannot do without is that employees can identify their own peak hours, option 1.