The correct option is
B Volvox - Hydrilla - Pistia - Scirpus - Lantana - OakSuccession is a process by which the biological community in an area changes with time. Hydrological succession is an important phenomenon which has following stages
(i) Phytoplankton Stage - This constitutes the pioneer community. Some blue-green algae, diatoms and bacteria etc. are the first organisms to colonise the primitive medium of the pond.
(ii) Rooted Submerged Stage - As a result of death and decomposition of phytoplankton and their mixing with the slit, brought from the surrounding land by rain waters and by wave action of pond water, there develops a soft mud at the bottom of the pond.
(iii) Rooted Floated Stages - They all are rooted hydrophytes with their large leaves floating on the water surface water level by now become very much decreased.
(iv) Reed Swamp Stage - This stage is also known as the amphibious stage. The plants have well-developed rhizomes and form very dense vegetation. The water level is by now very much reduced and finally become unsuitable for these plants.
(v) Sedge-meadow stage - The mesic conditions approach the area and marshy vegetation disappears gradually.
(vi) Woodland Stage - By the time of disappearance of marshy vegetation, the soil becomes drier for most time the year. Terrestrial plants now invade this area.
(vii) Forest Stage - This is a climax community. Several trees rapidly invade the woodland community.
So, the correct answer is option B.