Your project was just completed. Because of some unfortunate circumstances, the project was delayed, causing cost overruns at the end of the project?

I fully agree that product verification is the correct answer. 

D. Product Verfication is the correct answer

D. Product verification. Because after compeletion of project we can get the exact cost of material, transport, manpower, engineering, tools, site expences etc. Now if project was delayed then we can look for the reason behind that.

D. Product verification

Explanation:

Product verification involves examining the work of the project for completeness and correctness. This process occurs on the existing project and isn't of much benefit to future projects because. you'll perform product verification on future project work at the close of the project. By definition, a project is unique and creates a unique product or service.

In a project, unfortunate circumstances are known as a source of  "Risk" and they are very useful for successful completion of any important project. At the planning stage, we need to collect information about all possible Risks in the project from all possible sources, one of them is Lesson Learned Report of previous similar projects. So such information is very useful. 

In this specific case Cost estimating, Allocating Resources and Activity estimating are associated with Risk factor so at the time of project planning stage its input will be necessary to arrive at the best possible estimates. where as Product verification is an activity to be performed during execution of the project which is not associated with cost factor. So answer is "D".

My Answer is D. Production Verfication

The correct answer is Option D - Product verification. As kown these various costs could be normally verified during the project execution not after project completion.