Answer: Option C
Explanation: Manufacturing overhead refers to the that portion of the cost which cannot be allocated to the units produced in a reasonable manner. These costs are indirectly related to the product manufactured. For example = depreciation, rent etc.
Thus, the cost of glue cannot be allocated to each individual unit produced. As the worker might put a more in one unit and a little less in the other.
Thus, from the above we can conclude that the correct option is C.