In a population, a shift in the average population phenotype toward the mean and away from the physical extremes. this process lowers phenotypic variety; the population is more homogeneous.
i believe the answer is c. herbaceous or wood stems because the stem, hold up the flower and leaves into the sun light for energy/food.
the first process is called sea-floor spreading (rifting when it happens on land) and the second process is called subduction. both processes are part of plate tectonics.
can you paste a picture of the diagram?
d sounds more logical.