Question

what important nutrient for plants is concentrated in their roots by active transport? xenon chloride phosphate

Explanation:

Plants need essential nutrients, and phosphate is a key nutrient (part of ATP, DNA, etc.) taken up by roots via active transport. Xenon is a noble gas, not a plant nutrient. Chloride is a micronutrient, but phosphate is a major macronutrient concentrated via active transport for energy and structural roles.

Answer:

phosphate (the option with "phosphate" text, assuming the third option is phosphate as per the list: xenon, chloride, phosphate)