What are alleles ? anybody knows

The movement of tectonic plates in two different locations is shown below: two blocks labeled location a and location b are shown. at location a the top layer of the block shows two horizontal arrows pointing towards each other. small dunes are shown in the middle between the two arrows. the block labeled b has a vertical line in the middle. on the left of the line there is an arrow pointing down. on the right of the vertical line there is an arrow pointing up which statement is most likely true? subduction may occur in both locations. earthquakes may occur in both locations. subduction may occur in location a only and a volcanic eruption may occur in location b only. an earthquake may occur in location a only and a volcanic eruption may occur in location b only.

Consider the model of the oxygen cycle on earth. the majority of earth's oxygen reservoirs are found in the a) atmosphere. b) biosphere. c) hydrosphere. d) lithosphere.

What organelle other than the nucleus houses dna in a eukaryotic cell?