An antigen triggers a response from the immune system and an antibody is produced. All antibodies are immunoglobulins, therefore, the correct answer is immunoglobulin. More specifically, an immunoglobulin is a protein produced by plasma cells to fight and neutralize pathogens. To do so, the immunoglobulin has a specific region which is complementary to a specific region of the antigen. Immunoglobulin's mechanism of action is to bind to the pathogen and either block its action or trigger a response of other cells of the immune system.
Your question is rather unclear but from what I can tell either there were not an even amount of Petri dishes or some of them were left open while others were not.
I’m not 100% sure what you are asking for but here is my explanation
The grouping of objects helps the shopkeeper because now the shopkeeper can find where everyone is faster. This will ultimately make taking inventory easier. As a result the efficiency of the shop and the shopkeeper will be faster. An efficient shop will result in better sales and overall will make the shop better.
