The correct option is B Spirogyra
Algae can be found in freshwater and marine water. Green algae are mostly found in freshwater. here only Spirogyra is an example of green algae. Sargassum and laminaria are the brown seaweed/algae found in brackish or salt water. They are rarely found in freshwater. Polysiphonia are red algae which are found in salt water. Therefore correct option is D "Spirogyra"