b. Wrong. Cells that don't incorporate the transfected DNA should die, because they lack the gene for G-418 resistance.
c. Possible - in this case Ronnie should repeat the experiment using a new stock of antibiotics of the appropriate concentration. (Check answer D too.)
d. Possible - Ronnie should check whether:
e. Possible - we hope that is the case.
f. Possible. Only further analysis will reveal whether these cells actually incorporated the transfected DNA.