Significance of treating bacterial cells with calcium chloride before transformation is to facilitate

Refer to the following statements for agarose-gel electrophoresis:
$(a)$ The $\text{DNA}$ fragments resolve according to their size.
$(b)$ The separated $\text{DNA}$ fragment can be visualised only after staining with ethidium bromide followed by exposure to $UV$ radiation.
$(c)$ $\text{DNA}$ is always loaded into the well.
$(d)$ The smallest fragment of $\text{DNA}$ is near the well.
Choose the correct statements:

The figure below shows three steps $(A, B, C)$ of a process. Select the option giving the correct identification $:-$

If a recombinant $DNA$ bearing a gene for resistance to Ampicillin is transferred into $E. coli$ cells,the host cells become transformed into Ampicillin-resistant cells. What happens when these $E. coli$ are grown on a medium containing Ampicillin?

Downstream processing includes:
$I.$ Separation of the product from the reactor
$II.$ Purification of the product
$III.$ Formulation of the product with suitable preservatives
$IV.$ Quality control testing and clinical trials in case of drugs
Which of the statements given above are correct?

When $DNA$ fragments stained with ethidium bromide are viewed under $UV$ radiation,how do they appear?