Air circulates in Earth's atmosphere. What is the fundamental cause of air circulation in
Earth's atmosphere?
a. ocean currents
b. energy from the sun
d. earth’s magnetic field
i have to have where i found the answer on, so if you have the hmh sixth grade book it will help.

Molecular models of two different substances are shown below. in the molecule on the left, the oxygen atom pulls on electrons more strongly than the hydrogen atoms. in the molecule on the right, the two oxygen atoms pull on the shared electrons with the same strength. water molecule, h,o oxygen molecule, oz when the two substances are put in the same container, they do not attract each other. why does this happen? a. they both contain oxygen. b. one is polar and one is nonpolar. c . they are both polar. d. they contain different elements.

You are observing different types of cells in your science lab. one cell has many chloroplasts. what is the most likely function of this cell? a. energy production b. photosynthesis c. reproduction d. digestion

There are fewer than 100 naturally occurring elements in the universe, but there are millions of different unified substances. explain how this can be true.