The richest sources of vitamin $B_{12}$ are

Chloramphenicol and erythromycin (broad-spectrum antibiotics) are produced by

$A$: Microbes have been used for the welfare of humanity.
$R$: The fields of biotechnology and genetic engineering have developed.

Consider the following statements:
$I.$ Antibiotics are chemical substances produced by some microorganisms which can kill or retard the growth of other disease-causing microorganisms.
$II.$ Penicillin is the first antibiotic discovered by Alexander Fleming $(1928)$,while working on the bacterium $Staphylococcus$ $aureus$.
$III.$ The function of penicillin as an antibiotic was established by Ernst Chain and Howard Florey.
Which of the statements given above are correct?

Which of the following statements is false regarding microorganisms?

Microbes like ............ can be grown easily on material like waste water from potato processing plants (containing starch).