The Supply of Labour to an Industry Is Generally Upward

The supply of labour to an industry is generally upward sloping because:

A) The substitution effect and the scale effect of a wage change work in the same direction.
B) The wage elasticity of labour supply is elastic.
C) There are many workers working for an industry.
D) It is more profitable for firms to hire more workers when labour is cheap.
E) Workers are more willing to work when there are added incentives in the form of higher wages.