40. Plant roots that are in a horizontal position grow down because (A) cells on the upper side elongate more than those on the lower side. (B) auxins are stimulating cells on the lower side to elongate more. (C) auxins are being pulled to the upper side. (D) auxins are having no influence on this process.

48. You are studying the bacteria in the water of a nearby pond. From a 100 mL sample, you use a 0.5 mL subsample to inoculate a plastic dish filled with a semisolid nutrient medium that fosters growth of coliform bacteria. After an appropriate incubation period, you count 100 bacterial colonies growing on the surface of the medium. What conclusion can you make about the coliform bacteria in the pond water? (A) There is approximately one coliform bacterial cell per milliliter. (B) There are approximately 200 coliform bacterial cells per milliliter. (C) There is approximately one coliform bacterial species per milliliter. (D) There are approximately 200 coliform bacterial species per milliliter.

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