Which of the following sentences is written correctly?
a) The American Civil War, that was fought over one hundred and fifty years
ago, killed more Americans than any other war.
b) The American Civil War that was fought over one hundred and fifty years ago
killed more Americans than any other war.
c) The American Civil War, which was fought over one hundred and fifty years
ago, killed more Americans than any other war.
d) The American Civil War which was fought over one hundred and fifty years
ago killed more Americans than any other war.