The article “Growth Response in Radish to Sequential and Simultaneous Exposures of NO₂ and SO₂” (Environmental Pollution [1984]: 303–325) compared a control group (no exposure), a sequential exposure group (plants exposed to one pollutant followed by exposure to the second four weeks later), and a simultaneous-exposure group (plants exposed to both pollutants at the same time). The article states, “Sequential exposure to the two pollutants had no effect on growth compared to the control. Simultaneous exposure to the gases significantly reduced plant growth.” Let 

and represent the sample means for the control, sequential, and simultaneous groups, respectively. Suppose that 

Use the given information to construct a table where the sample means are listed in increasing order, with those that are judged not to be significantly different underscored.

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X1, X₂, and X3