ADEA cases use the "but for" standard when deciding if age discrimination occurred; whereas Civil Rights cases use a "mixed motives" standard when deciding if discrimination occurred. What is the biggest difference between the two?

The mixed motives standard means the employee's group membership was the only factor

The mixed motives standard means the employee's group membership was a factor, but not the only factor

The but for standard means that the employee has to show a bona fide occupational qualification $($BFOQ$)$

None of the above