Critical Reasoning

Brown tides are growths of algae on the sea’s surface that prevent sunlight from reaching marine plants below, thereby destroying not only the plants but also the shellfish that live off these plants. Biologists recently isolated a virus that, when added to seawater, kills the algae that cause brown tides. Adding large quantities of this virus to waters affected by brown tides will therefore make it possible to save the populations of shellfish that inhabit those waters.

Which of the following, if true, provides the most support for the conclusion of the argument?

A. When applied in large quantities, the virus not only kills the algae that cause the brown tides but also many harmless kinds of algae.
B. Marine animals that prey on shellfish avoid areas of the sea in which brown tides are occurring.
C. The number of different kinds of virus present in seawater is far greater than many marine biologists had, until recently, believed.
D. The presence of large quantities of the virus in seawater does not adversely affect the growth of marine plants.
E. The amount of the virus naturally present in seawater in which brown tides occur is neither significantly greater nor significantly less than the amount present in seawater in which brown tides do not occur.

D