The first crusade is the attempt to recapture the Holy lands from the assaults of the Muslim invaders. There are three reasons in this movement naming: 1) to give freedom to Jerusalem and the Church of the Holy Sepulchre; 2) to defend the suffering Christians of the East and (3) to marshal the energy of the feudal lords and knights into a unified warfare. Among these reasons, the related ones is the invasion of Muslim Arabs in Europe. Answer is B.