Is it (E)?

From the text we know "false chicory
plants that receive greater than twice the average rainfall of
the species' usual habitat always reach above-average"
"Always" is a key.

I picked E

But D seemed pretty close as well.

But in D, I felt the assumption was that "only" rainfall is a factor of plant height. this may not be true, not present in the text.

So I picked E. Anybody any light?
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I went with A. What is the OA?

i pick B here. i think B is the direct pre-phrase of the last sentence of the stimulus. whats the OA and source?
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The argument that contains many words makes the question become harder to solve. To make the argument easier. I will define the "False chicory plan" = X

=> Argument Evaluation: X's taproot = 1/2 X
Furthermore, the more rain X get, the taller X is
In fact, X that receives >2 average rainfall of usual reception is higher than the average height of X

(A) If two false chicory plants differ in height, then it is likely that the one with the shorter taproot has received less than twice the average rainfall of the species' usual habitat. => If 2 X differ in height, then it is likely that the X1 (shorter taproot) has received less than 2 average rainfall of X
=> These matter are not mentioned in the argument.
(B) If a false chicory plant has a longer-than average taproot, then it is likely to have received more than twice the average rainfall
of the species' usual habitat.=> If X's taproot is longer than X's average taproot, then it is likely to have received more than twice the average rainfall => This was stated in the argument. If you choose this choice as the correct answer. It's a trap. This answer is the reverse form of the argument.
(C) It is not possible for a false chicory plant to receive only the average amount of rainfall of the species' usual habitat and be of above
average height. => not mentioned
(D) If the plants in one group of false chicory are not taller than those in another group of false chicory, then the two groups must have
received the same amount of rainfall. => not mentioned
(E) If a false chicory plant receives greater than twice the average rainfall of the species' usual habitat, then it will have a longer taproot than
that of an average-sized false chicory plant. => If X receive >2 rainfall of the average X, then X will have longer than average (+ height of taproot = exactly 1/2 height of X) => the X'taproot will be higher than the average that of average X
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According to tuanquang269's reply, B and E are correct.

Is this a valid GMAT question ? Because GMAT won't support 2 choices. Any expert replies ?