Finished planning and have begun executing the project when the client asks if you would add some important features to the product of the project.

4.  Time and cost may both be affected

Option No.4

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Thanks

My answer is option (4)  Time and cost may both be affected

Option4 is the Answer for this Question.

No 1 - Scope and quality would be affected but not the cost.

1. Adding features will require additional cost but not time