When there is only funding available to improve one step in a process? $($Multiple Choice Answer but select $1$ best answer only$)$

A$.$ It should be the step that, after improvement expenses, results in the highest contribution.

B$.$ It should always be the first step, because quality should start at the beginning.

C$.$ It should always be the most expensive step.

D$.$ It should always be the last step, because more value$-$added is scrapped there.