Biology. The genes that people are born with account for about 50 % of a person's chance for addiction. , use "is" if the individual continues to be within the function/partnership you are discussing, and "was" if they don't seem to be in that purpose/partnership anymore. I hardly ever see https://directory4search.com/listings13332181/the-smart-trick-of-drug-rehabilitation-centre-in-islamabad-that-nobody-is-discussing