I believe it would be D. A copier, because in PCR the main goal is to amplify DNA sequences by producing many many copies of sections of DNA.
D - birth control is the most widely accepted method
The three conditions that should be present in order for a deadlock to be possible would be first the mutual exclusion which means a process can use one resource at a time. Second is hold and wait which means a process may need to hold the resources while waiting for the assignment of the other resources and lastly is no preemption which means no resource should be remove from a process that is holding it.
The answer should be D. Electrons