You are the test lead of a project. Your project is in the test execution phase and the customer comes up with an observation that the test case productivity of the team has reduced and wants an explanation from you. On analysis you find that your testers are spending a lot of time in re$-$testing the defects. How would you quantify your finding?

What is the correct answer $-$

a$.$ Showcase quality of the defect fixes metric to the customer

b$.$ Showcase test effectiveness metric to the customer

c$.$ Showcase application's defect density metric to the customer

d$.$ Show case effort variation metric to the customer