You are the lucky student of a wacky professor who develops a time machine. he asks if you will test it with him. you get in, and there is an immediate glitchthe date readout fails so that when you land, you are not sure what era you are in. as your time machine lands, you see an unusual landscape before you. as you open the door, you realize you cannot breathe. you quickly shut the door, realizing you are in the

The answer is the Archean Eon.

Explanation:

This period of history occured 4,000 to 2,5000 million years ago. Regarding its atmosphere, it is believed to have been almost completely oxigen-free. The Sun presented approximately 3/4 of its current luminosity, but the heat levels were nearly those of modern Earth.

It is believed that is was during this period that life began to exist on Earth, due to the Earth's crust gradual decrease in temperature.

b) to encourage free trade