The correct answer is option 1, Wolffia. Wolffia is known as the smallest flowering plant in the world. It is a type of aquatic plant that belongs to the duckweed family. Wolffia plants are tiny, measuring only about 0.1 to 0.2 millimeters in length. They have no roots, stems, or leaves, and they float on the surface of water. Despite their small size, Wolffia plants do produce flowers for reproduction. The flowers are so small that they are usually not visible to the naked eye. However, under a microscope, the flowers can be observed. Wolffia plants are found in freshwater habitats all around the world.