The best answers are deletion and insertion
Cooperation helps because they both defend each other. its a friendship that allows for living longer. For example, Near sharks, fish stay behind them, so that they are not killed, thats one example.
The reason why you cant test the activity of Lipase in test tube 5 is because in test tube 5 the PH is low. This decrease in pH might make it difficult to detect the activity of lipase since the optimal ph of pancreatic lipase is around 8.0. generally high or low PH result to complete loss of activities of most enzymes.
B. I think correct answer
Annelids skeleton is your answer
