The objective of a statistical process control (spc) system is to a. assess customer expectations. b. provide a statistical signal when natural causes of variation are present. c. eliminate natural variations. d. provide a statistical signal when assignable causes of variation are present.

D) Provide a statistical signal when assignable causes of variation are present.

Explanation: Statistical process control(SPC) is the method which controls the quality of the  process by using the statistical measures of analyzing and managing. The aim of SPC is generating a signal of statics towards the presence assignable reason of variable .

Other options are incorrect because it does not reduce the natural variations, works for assignable causes rather than natural causes and does not fulfill the consumer's requirements.Thus, the correct option is option(D).

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