How can purified $DNA$ be precipitated from a solution after appropriate treatment?

In a mixture,$DNA$ fragments are separated by

Which of the following processes is $NOT$ a part of the downstream processing?

Which of the following is not the application of $\text{PCR}?$

With respect to $DNA$ fragmentation:
Statement $A$: Gel electrophoresis and elution are two important processes.
Statement $B$: After staining with ethidium bromide,it has to be exposed to $UV$ light.

Which system is not present in a bioreactor?