I feel as if the best answer would be "Chocolate is now a sweet treat that is very popular in the United States." The first statement tells that it is popular in the United States. The second statement says that it hasn't always been a sweet treat. In the answer choice, it says "now", showing that it hasn't always been a sweet treat, but it is now.
Try to write it from the cockroaches point of view, almost as if the people invaded the cockroaches space and came into his/her home. End it with a dramatic scene following the discovery of the roach have fun with it.
