When Did Zoroastrianism Suffer a Major Blow

When did Zoroastrianism suffer a major blow?

A) In the first century CE when Christianity made inroads into Persia
B) In the fourth century BCE during the reign of Alexander the Great
C) In the seventh century when the Sasanian ruler surrendered to Arab Muslims
D) In the first century BCE when the Sasanian ruler was defeated by Augustus
E) In the third century CE when Mani's teachings supplanted Zoroastrianism