"extolled" means to praise some thing highly.
The answer is: Popular fashion concepts are established in Paris and New York before becoming popular elsewhere.
This because contagious diffusion refers to the spread of anything to multiple people whether it's ideas, beliefs, disease, etc..
Thus, things like fashion concepts are a prime example of a contagious diffusion since a fashion trend could start out in a place like Paris or New York and then spread throughout the whole fashion world influencing the direction of many fashion concepts and trends around the globe.
3. It will freeze. As a liquid becomes cooler the chances of it freezing goes up
