The events which occur in the water body after it has been polluted by fertilisers are given as follows:
(i) Submerged algae perish
(ii) Algae undergo sudden proliferation
(iii) Consumers such as fish die
(iv) Oxygen levels fall
(v) Bacteria act on the increased number of dead organisms.
Arrange them in a correct sequence.

Options

A. (ii)-(i)-(iii)-(v)-(iv)
B. (iii)-(iv)-(i)-(ii)-(v)
C. (ii)-(i)-(v)-(iv)-(iii)
D. (i)-(iv)-(v)-(iii)-(ii)

Explanation

To arrange the events that occur in a water body after it has been polluted by fertilizers in the correct sequence, we can follow these steps:

1. **Algae undergo sudden proliferation**: When fertilizers enter the water body, they provide nutrients that lead to a rapid increase in the growth of algae. This is the first event that occurs.

2. **Submerged algae perish**: After the initial proliferation, the algae eventually die due to various factors such as lack of light or nutrients. This is the second event.

3. **Bacteria act on the increased number of dead organisms**: Once the algae die, bacteria begin to decompose the dead algae, leading to an increase in bacterial population. This is the third event.

4. **Oxygen levels fall**: As bacteria decompose the dead algae, they consume a significant amount of oxygen in the water, leading to a decrease in oxygen levels. This is the fourth event.

5. **Consumers such as fish die**: Finally, with the oxygen levels depleted, aquatic organisms such as fish cannot survive, leading to their death. This is the fifth event.

So, the correct sequence of events is:
1. Algae undergo sudden proliferation
2. Submerged algae perish
3. Bacteria act on the increased number of dead organisms
4. Oxygen levels fall
5. Consumers such as fish die