The four main systems of earth are
a. geology, meteorology, oceanography, and chemistry
b. geosphere, atmosphere, hydrosphere, and aerosphere c aromatherapy, biology, chemistry, and properties d geosphere, atomosphere, hydrosphere, and biosphere

I think is alternative a because that includes the earth

Europe needs to build a trump-like wall that will spread across europe making it impossible for migrants to cross they need to spread pig guts all over this wall so the muslims will never consider crossing into europe..you might be asking "can't they just fly over with planes? " well yes they can so we will install thaad missile protections system to shoot down any aircraft that violates europe's air fourth would be to start a fourth reich in germany.. last but not least.. make europe great again!

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.