There are n cities. What is the number of airlines that connected 7 different cities (airline from city A to city B is different with airline from city B to city A)?	Choose the correct choice:
A) n(n-1)
B) n(n+1)
C) n(n-1)/2
D) n(n-6)
E) n2
First of all, the possible number of airlines is n. Then, the possible number of airlines departing from one city to another becomes (n-6). Hence, the answer is n(n-6), which makes A an answer choice.   n(n-6)
<result>D</result>
There are n cities. What is the number of airlines that connected 7 different cities (airline from city A to city B is different with airline from city B to city A)?