Explanation
A. The argument does not specify that employers only act in a morally reprehensible manner when they harm their employees.
B. The argument does not claim that no employers who use their employees as a means to an end act morally.
C. (Correct Response) The argument implies that treating employees fairly is compatible with using them as a means to an end. For the conclusion that using others as a means to one's own ends is not always morally reprehensible or harmful to be valid, it must be assumed that at least some employers who treat their employees fairly are still using them as a means to their own ends.
D. The argument does not directly deal with the specifics of making a profit from labor; it speaks more broadly about the moral implications of using others for personal ends.
E. The argument does not hinge on the impossibility of harm without using someone as a means to
an end. It suggests that using someone as a means to one's own ends can occur without it necessarily being harmful or morally wrong.
The assumption that the argument requires is option C. This assumption underlies the argument's conclusion that using others as a means to one's own ends can be done in a manner that is not morally reprehensible or harmful, as evidenced by the fair treatment of employees by many employers.