Alice is studying how human activities impact ecosystem biodiversity in her college class. Her latest assignment is to design and test a model that will demonstrate a method to reduce the environmental impact of a specific human activity.

Alice notices that a local farm is situated on the edge of a river. She then confirms that chemical fertilizers are entering the river ecosystem through surface runoff, potentially harming aquatic wildlife and reducing biodiversity.

farm situated near a river
Alice decides to build a functional scale model to see if it can reduce the amount of fertilizer entering the river. After explaining her assignment to the farm's owner, she is granted permission to design and test her model at the site.

Which design would best fulfill Alice's assignment?

A.
mark off a 10-foot-wide strip of land between the farm and the river and transplant closely-spaced perennial vegetation there
B.
dig a six-inch-wide channel from the farm to the river in order to concentrate the surface runoff and limit the exposed area
C.
build a one-foot-tall retaining wall out of sandbags around the farm to prevent surface runoff from reaching the river
D.
section off a 100-square-foot area of the farm and ask the farmer to use twice the normal amount of fertilizer there

Rease is an enzyme used by plants to break down urea (a nitrogen-containing compound) into carbon dioxide and ammonia. urease urea > > > carbon dioxide and ammonia ammonia is broken down by plants into a nitrogen source plants need to grow. thus, plants could not use urea as a nitrogen source unless it was first converted to ammonia. in soybean plants there are two different kinds of urease, one produced in the seeds and the other produced in the leaves of the plant. three types of soybean plants were used in a set of experiments: normal soybeans and two mutant strains, one lacking the urease in the seeds only (strain 1) and one lacking urease in the leaves only (strain 2). experiment 1 separate areas in a field were planted with normal, strain 1, and strain 2 soybeans. all types of soybeans appeared to grow, flower, and produce seeds equally well. there were no externally detectable differences among the strains. experiment 2 small pieces of plant leaves of equal weight were obtained from each type of soybean plant and separately placed on media in culture dishes. tissue growing in this way will become an unorganized clump of cells referred to as callus. to provide a controlled nitrogen source, half the tissue samples of each type were placed on media containing urea, and the other half of the samples were placed on media containing ammonia. after 30 days, the weight gain for each of the callus samples was determined. results are shown in the table below.