The time to manufacture product is 8 hours in the first month , this time increase in the second month to 6 hours this is example of

c- it is learning curve example

Learning curves reflect the increased rate at which people perform tasks as they gain experience.

In the given question in the First month It took8 hours to manufacture a product; where as in the second month it took only6 hours.

Hence the answer option is: LEARNING CURVE.

NOTE: IN THE QUESTION INSTEAD OF THE OPTION TO MENTION AS 'DECREASE' IT WAS MENTIONED AS "INCREASE"  ...........................  i THINK IT REQUIRE CORRECTION.