@Molpoing D.Last summer Jim mowed just one lawn, but now he mows three that dose not correct the run on sentence.
Answer:
I'm not sure if this will make sense, but there isn't really a limit on quotes in an essay, obviously you shouldn't make a paragraph littered with them, but I would say at least 2-3 depending on the length of a paragraph.
In which the populations at risk have had no previous contact with the diseases that strike them and are therefore immunologically almost defenseless
D is incorrect, because, assuming George Eliot is speaking, there would be quotation marks after the first comma and then before “is”.