Samples X, Y and Z are epidermal tissues cut from an onion. Each epidermal tissue was immersed in one of three different concentrations of a salt solution for 30 minutes. A student observed each tissue sample with a light microscope. Then the student estimated the concentration of each salt solution using a scale. The diagram shows the scale. P, Q and R represent the estimated concentration of the three salt solutions. [Figure 18.1 (scale diagram from distilled water to concentrated salt solution with points P, Q, R)] The photomicrographs show the appearance of the tissues in samples X, Y and Z. [Figure 18.2 (photomicrographs of sample X, sample Y, sample Z)] Which row shows the estimated concentrations of the salt solutions in which samples Y and Z were immersed?

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