How might the natural forces of the western hemisphere change in the future

As our current atmosphere formed, the concentrations of various atmospheric gases fluctuated. match each gas with the explanation that best describes how its proportion changed during the evolution of the atmosphere.

Bonus question: according to wikipedia, in chinese philosophy yin and yang "describes how seemingly opposite or contrary forces may actually be complementary, interconnected, and interdependent." what are some examples from the story that amy tan may have intentionally incorporated elements of yin and yang philosophy into this story? select 2.

Read the aphorisms. be slow in choosing a friend, slower in changing. an open foe may prove a curse; but a pretended friend is worse. a true friend is the best possession. according to these aphorisms from benjamin franklin's poor richard's almanack, what might happen if a person is careless in choosing a friend? it is best not to have friends because they will usually betray you. casual friends are often the best and can be more trusted than enemies. a person who has betrayed you can sometimes become a good friend. a friend who is not carefully chosen can be worse than an enemy.