John and Mark Hold Equivalent Secretarial Jobs,but John,who Makes 20

Multiple Choice

John and Mark hold equivalent secretarial jobs,but John,who makes 20 percent more than Mark,is employed by a manufacturing firm while Mark is employed by a department store.Based on this information,which of the following best explains this pay differential?

A) interindustry wage differentials
B) differences in human capital intensity
C) merit exception of the Equal Pay Act of 1963
D) John's stronger negotiation skills