Arrange the following in the decreasing order(most important first) of their importance, for the welfare of human society. Give reasons for your answer.
Biogas, Citric acid, Penicillin and Curd.

Explanation

Penicillin, biogas, curd and citric acid.
Penicillin is the first antibiotic discovered by Alexander. Flemming. It is a potential antibiotic used to kill pathogenic bacteria. Now a days antibiotics have played a major role in controlling infectious diseases like dephtheria, whooping cough and pneumonia.
Today , we cannot imagine a workd without antibiotics.
Biogas produced by microbes is used as a source of energy in rural areas.
Curd is a nutritive food. In the stomach it plays a vital role in cheacking diseases causing microbes.
Citric acid is a good source of vitamin C.