In order to collect only bacterial cells that had taken up the plasmid successfully, a sample should be taken from A - VCE - SSCE Biology - Question 30 - 2020 - Paper 1

To select the appropriate plate for collecting bacterial cells that have successfully taken up the plasmid, we assume that the plates represent different growth conditions or treatments. Typically, Plate 3 would contain the colonies that have incorporated the plasmid and are expressing a selectable marker, such as antibiotic resistance. This allows for the identification and collection of only those bacterial cells that have successfully taken up the plasmid.