Estados Unidos y Canadá tienen bajas tasas de natalidad y mortalidad ¿Qué implica para sus gobiernos que sus poblaciones estén envejecidas?

Idk bro sorry  lava is hotter then magma but im  not sure about it alll

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. 

What do i have to choose from? what are the answer choices? .