单项选择题
An organisation manufactures a single product. The total cost of making 4,000 units is 
40,000. Within this range of activity the total fixed costs remain unchanged.
What is the variable cost per unit of the product?
A．$0.80
B．$1.20
C．$1.25
D．$2.00
B．$1.20
C．$1.25
D．$2.00