Hint: The slime mold is the eukaryotic organism that freely lives as a single cell in the external environment. When the situation comes, millions of unicellular organisms join together to form multicellular reproductive structures. These organisms are considered as the fungi but not included under this kingdom.
Complete Answer: - In the given option, the physarum is only considered as the slime mold or the myxomycete. It does not have cells and hence they are called as acellular slime. They mainly grow in the dark places and they eat the other microorganisms like the bacteria, fungi spores etc. They are yellow in color. - Thiobacillus is the gram negative bacteria and has the ability to tolerate the extreme concentrations of ions like iron, copper, zinc etc. - Since they oxidize these ions and survive. The Anabaena azollae is the phototrophic cyanobacteria that prepare its own food with the help of the vegetative cell in them. - The Rhizopus is the fungus that is saprophytic in nature live on the plants. Hence the physarum is the only slime mold among the options given.
Thus the option (A) is correct.
Note: The anabaena maintains the symbiotic relationship with the azolla. Since the anabaena produce its food, it offers nitrogen to the azolla fern, where the azolla provides the habitat for the survival of the anabaena. Hence the azolla is used as fertilizer in the rice.