Which sentence is punctuated correctly?

a.
my father has studied these languages: russian; german; and arabic.

b.
on their vacation trip to europe, the richardsons visited vienna, austria; munich, germany; and warsaw, poland.

c.
the dates of the big conventions are may 18-20; july 13-15; and august 17-19.

d.
james city county; virginia, st. mary's county; maryland, and york county; maine are some of the oldest counties in the united states.

What effect is created by the plaque posted on the gate at the entrance to the family's home in nadine gordimer's "once upon a time"? the words written on the plaque offer readers a foreshadowing of the story's outcome without revealing the actual conclusion, the author's use of flashback allows readers to understand what is at the heart of the issues of encroachment in the suburban neighborhood the repetition of the words written on the plaque presents an oxymoron because readers already sense that the plaque has been ineffective in warding off intruders. the author introduces a paradox in which readers are presented with a warning notice when no actual infraction has taken place.