Concept:The most significant rite for the would-be couple is the Nikah, the Islamic marriage ceremony itself.Explanation:The Nikah is the religious ceremony in which the couple officially accepts each other as husband and wife under Islamic law.It is the essential and valid way for a Muslim man and woman to be married.Other practices such as Istikhara, Walima, and Aqd are connected to marriage, but the Nikah is the actual binding rite for the couple.Answer:C. Nikah