The correct option is A Filaments are slippery to touch
The plant body of Spirogyra is an unbranched filamentous thallus, measuring about 1 m in length. The Spirogyra filament is very slimy due to the presence of mucilage sheath that lines the whole filament. The mucilage often holds the filaments together in a matted blanket. Hence, Spirogyra is commonly known as pond silk, water silk, pond scum or mermaid’s trees because of their bright green silky appearance.