Atransaction in one party in the relationship benefits at the expense of the other.

martians or other types of aliens represent a unique fear as opposed to zombies. vampires and other types of monsters.   in most sci-fi stories, aliens come from other worlds and have different or more advanced technology.   abductions and experimentation on human bodies that involve these technologies, or the use of these technologies against human beings and the use of unknown "powers", are a type of fear that's different from that of other types of monsters.  

government played the key role in promoting industrialization in russia while individual businesses played a larger role in great britain. or for apex a