4. A teacher sprinkles some iron shavings on a clear tray. She places two magnets in the shavings with the north ends facing each other. (See the picture below here before move on) Based on the cause-and-effect relationship between the magnets, which phenomenon is the teacher modeling for her students? MS-PS2-3 a. electrical force
b. attractive force
c. field of repulsion
d. gravitational attraction

The gene that causes sickle-cell disease is present in a higher percentage of residents of sub-saharan africa than among those of african descent living in the united states. even though this gene causes sickle-cell disease, it also provides some protection from malaria, a serious disease that is widespread in sub-saharan africa but absent in the united states. discuss an evolutionary process that could account for the different percentages of the sickle-cell gene among residents of the two regions.

Variety of living organisms; includes genetic, species, and ecological types.

Ecologist have observed a sharp increase of sulfur dioxide in the air . what might be a possible consequence of excessive sulfur dioxide in the air ? a. acid rain b. ozone layer depletion c.ozone layer hole d.increase in sea levels