> > > which sentence best shows correct comma usage?
a. native american groups include the mayan the aztec, and the toltec people. b. native american groups include the mayan, the aztec and the toltec people. c. native american groups, include the mayan the aztec and the toltec people. d. native american groups include the mayan, the aztec, and the toltec people.

there's only 5: 00 to complete answer can i comment

here is the essay.

global warming. are we heading to a mini ice age era?

everybody have heard about the effects of global warming on planet earth. but in recent studies, many scientist explain that it is not the human being and his pollutants, what is affecting the planet. that only represents a small part. they make reference that what we are living on the planet right now is one of the many cycles of planet eart through its existence. because human life is too short, we do not stay on the planet too long to see its effects.

people everywhere should be concerned, but the clarion call is for the youngster to hear it.

some russian scientist has stated that the last mini ice age era was in the 1700's and people survived. they had a brutal winter in europe. even the thames river in london, partially frozen, but humanity knew how to keep on.

that is the lesson. humanity must take consciousness and prepare for a cold future, not a warm one.