Monoecious plants of Chara shows occurrence of Antheridiophore and archegoniophore on the same plant. Stamen and carpel on the same plant. Upper antheridium and lower oogonium on the same plant. Upper oogonium and lower antheridium on the same plant.

Monoecious plants are those species that bear both sperm and eggs on the same gametophyte. Chara is a genus of green algae in the family Characeae. They are multicellular and superficially resemble land plants because of stem-like and leaf-like structures. They are found in freshwater, particularly in limestone areas throughout the northern temperate zone, where they grow submerged, attached to the muddy bottom. They prefer less oxygenated and hard water and are not found in waters where mosquito larvae are present. They are covered with calcium carbonate deposits. Chara is a genus of green algae in the family Characeae. They are multicellular and superficially resemble land plants because of stem-like and leaf-like structures. They are found in freshwater, particularly in limestone areas throughout the northern temperate zone, where they grow submerged, attached to the muddy bottom. They prefer less oxygenated and hard water and are not found in waters where mosquito larvae are present. They are covered with calcium carbonate deposits. Hence, Option D is correct.