Which of the Following Is an Example of Specialization

Which of the following is an example of specialization?

A) The output of workers in a chocolate factory doubling when a new manager was appointed
B) The cost of production of a light bulb making factory decreasing as its capacity increased
C) Different workers in a shoe factory being allotted different parts of shoe making instead of a worker making an entire shoe
D) The import of better technology and machinery from developed countries greatly increasing the number of laser printers manufactured by a company