The Primary Reason Why Workers in the Fast-Food Industry Are

The primary reason why workers in the fast-food industry are paid less is that:

A) These workers are seldom unionized.
B) These workers collect economic rents.
C) The demand for the product that they produce is quite elastic, making the demand for labour wage elastic.
D) It is easy to substitute capital for labour in the industry, making the demand for labour wage elastic.
E) Labour costs comprise a large share of the employer's expenses, making the demand for labour wage inelastic.