Algae  are very simple plants. They grow in fresh water or salty water. Seaweed is algae that grow in salty water. Seaweed is red or brown in color. The Japanese people use these plants from the sea in many ways. From it, they make a food called Kombu. Kombu is seaweed that has been dried, cooked and pressed together. Then it is dried again and cut into long pieces. The Japanese eat a lot of Kombu and like it very much. Japanese farmers often use seaweed as fertilizer. It makes their plants grow better. Many farmers also find seaweed makes a fine food for their animals. From seaweed the Japanese also get iodine , which they sell to other countries. Iodine is used in many ways all over the world. It is used in making medicine. It is added to the salt we use at the table. Scientists even use one form of iodine to "seed clouds" when they want rain to fall. In the last sentence of the text, "seed clouds" means   _  .
clouds spreading like seeds to make rain fall with human power the seeds like clouds dropping seeds by clouds