单选题 Two experimental garden plots were each planted with the same number of tomato plants. Magnesium salts were added to the first plot but not to the second. The first plot produced 20 pounds of tomatoes and the second plot produced 10 pounds. Since nothing else but water was added to either plot, the higher yields in the first plot must have been due to the magnesium salts.
Which of the following, if true, most seriously weakens the argument above?

A、 A small amount of the magnesium salts from the first plot leached into the second plot.
B、 Tomato plants in a third experimental plot, to which a high-nitrogen fertilizer was added, but no magnesium salts, produced 15 pounds of tomatoes.
C、 Four different types of tomatoes were grown in equal proportions in each of the plots.
D、 Some weeds that compete with tomatoes cannot tolerate high amounts of magnesium salts in the soil.
E、 (E) The two experimental plots differed from each other with respect to soil texture and exposure to sunlight.

【正确答案】 E

【答案解析】[解析] 本题属于典型的“B，A”型，由一experiment得出结论，且结论用来解释experiment，寻求反对，多为“有其他原因”。(E)指出这两块试验菜圃的土质与日照量不同，从而用“有其他原因”解释了第一块菜圃较高产量的原因。所以(E)正确。