There is not a specific antonym for diaspora, but the opposite of a diaspora would be the regrouping of a community or the coming together of a community. It could also be a renewal of a specific cultural group or ethnicity coming back together in a sort of revival of their culture.
C because there normally is a national army whose first duty is to protect
The answer is most likely c.
Emerge, emanate, issue mean to come forth. Emerge is used of coming forth from a place shut off from view, or from concealment, or the like, into sight and notice: The sun emerges from behind the clouds.
I believe that the best answer would have to be B. statistics<span> on the number of plane crashes and near crashes</span>