Question

In B.O.D test, oxygen plays an important role to
(A) Destroy pollution
(B) Destroy inorganic matter
(C) Destroy waste organic matter
(D) None of these

Answer 1

Hint: There is a relation between biological oxygen demand and dissolved oxygen. Generally, on exposure to toxins, biological oxygen demand increases. Since cold water holds onto oxygen better than warm water does, dissolved oxygen levels are often lower in the summer. The high amount of organic materials in a lake can lead to the higher BOD and lower dissolved oxygen.

Step by step solution:

The term "biochemical oxygen demand" (BOD) refers to how much oxygen is used by bacteria and other microorganisms during the aerobic (oxygen-containing) decomposition of organic matter at a particular temperature. High amounts of organic pollution, typically brought on by inadequate wastewater treatment, can result in high biochemical oxygen demand. High nitrate levels can also result in high plant growth. There are two general stages of BOD. The carbonaceous stage is considered while determining the oxygen demand. Since this stage is nearly finished in 5 days, the majority of the sewage's organic content is oxidised under aerobic circumstances in 5 days. BOD for 5 days is therefore computed.
The rate at which oxygen in the stream is reduced increases with BOD. This implies that higher kinds of aquatic life have less oxygen available to them. The effects of the high BOD are the same as those of low dissolved oxygen: stressed, suffocated, and dead aquatic creatures. Conversely, a low BOD indicates that less oxygen is being taken out of the water, making the water in general purer. BOD stands for the amount of oxygen (mg/l) needed for one litre of garbage or other material to decompose by microbial processes (bacteria)
Therefore, option (C) is correct.
Note: Chemical oxygen demand (COD) is the quantity of oxygen needed to oxidize organic molecules, whereas biochemical oxygen demand (BOD) is the quantity of oxygen needed by microbes to break down organic materials.