Provide of single colonies when inoculation of media in Petri dishes used to:

<p style="text-align:left;"><strong>a- identification of bacteria</strong></p> <p style="text-align:left;"><strong>b- see whether a culture is pure or mixed</strong></p> <p style="text-align:left;"><strong>c- a &amp; b</strong></p> <p style="text-align:left;"> </p> <p style="text-align:left;"><strong>d- non of the above</strong></p>