An international group of zookeepers with successful breeding programs made the following animal exchanges last year. using the same bartering system, how many oryxes can a zoo obtain in exchange for 15 flamingos?

Answer carbon dioxide ice;

Humans have survived and thrived in mexico city by using technology to create greater access to land. when the spanish conquered the aztec capital, tenochtitlan, in the 16th century, they built mexico city by draining the lakes and filling in the lake water to create more arable land for agriculture. this technique of land reclamation has continued to be fundamental to human civilization in mexico city. 

The answer would be  b. hope this !