Alarge, new diamond mine has just opened, and the price of diamonds has gone dow. since she has studied eco onus, cecilia decides to buy a diamond necklace since she knows that

Cecillia has studied economics and knows that the price of diamond will keep going up over the years as demand is always  more than supply whether a new diamond mine is opened or closed,it does not matter much.

If we look at the historical price rise of diamond over the years we find that the price of diamond in 1960 was $ 2700 for 1 Carat which rose dramatically to $ 28400 in 2016 which is a rise of 28400/2700= 10.51 which means the price rose by more than 10 times over a period of 56 years.

That is why Cecillia bought a diamond necklace at a lower price as a diamond mine had opened but she knew that the price of diamond will go considerably high if she was able to keep it for 10 to 20 years or so or may be even more.

answer; /// i believe that the correct answer is(cognitive revolution);