The Average Work Week in the United States Has Declined

Multiple Choice

The average work week in the United States has declined to fewer than 40 hours even though wage rates have been increasing.The best explanation of this phenomenon is that

A) the labor supply curve shifted to the right
B) the labor demand curve shifted to the right
C) the income effect of rising wages outweighed the substitution effect
D) the income effect of rising wages could not outweigh the substitution effect
E) none of the above