To determine how many of the listed compounds are pesticides, we will examine each chemical individually:
D.D.T. (Dichloro-Diphenyl-Trichloroethane) D.D.T. is a well-known pesticide that was widely used for controlling insects in agriculture and is now restricted or banned in many countries due to its environmental impact. Thus, it is a pesticide.
Aldrin Aldrin is an organochlorine insecticide used for protection against soil pests such as termites and grasshoppers. Like D.D.T., its use is restricted in many places due to toxicity. It is another compound classified as a pesticide.
Sodium arsenite Sodium arsenite is primarily used as a herbicide to kill unwanted plants and weeds and can also be toxic to animals and humans. However, in the context of classification as a pesticide, it is primarily registered as a herbicide rather than an insecticide or a compound meant to control pests directly on crops. Hence, it does not count here as a pesticide in the traditional usage context.
Sodium chlorate Sodium chlorate is used primarily as a herbicide rather than an insecticide. It destroys unwanted vegetation and is highly effective in non-selective weed control. Hence, it does not fall under the typical pesticide category used for insect or pest control.
Based on the analysis, two compounds, D.D.T. and Aldrin, are classified as pesticides. Therefore, the correct answer is option 2.
