Concerning the prophecy in Isaiah 7:14 regarding a sign, what was the primary significance of the name 'Immanuel' ('God with us') in its immediate historical context?

A It was solely a reference to a future, distant Messiah, unrelated to Isaiah's time. B It was a symbolic assurance to King Ahaz that God would protect Judah from the immediate threat of Syria and Israel. C It was a prediction that a future king of Judah would be named Immanuel. D It signified the complete and utter destruction of all of Judah's enemies.