Wolffia is an aquatic plant and mostly found floating on the water. These kinds of don't have roots and also called as Watermeal whereas Chara is also an aquatic plant but this is found in Fresh water. Urticuleria is mostly found in wet soils but doesn't grow in polluted water. These are sub aquatic plants. So among those options, Option C Wolffia will be the answer to your query. These plants are generally called as Water Pollution Indicators as these plants grow in Fresh, polluted and Wet soiled which helps to understand if the water is contaminated or not.