What’s the answer for number 4?

I would like to say b but I’m not 100% sure. Some proteins are regulated by the non-covalent bonding of smaller molecules like amino acids and nucleotides and those cause a change in the conformation and whenever a protein is produced a copy of the DNA is made. DNA is what holds the information for making all the different proteins in your body. But why I think it’s b is by changing the sequence of nucleotides in the DNA molecule it can change the amino acids in the final routine and create a protein malfunction. So yeah I think it’s be because by changing the sequence of nucleotides it
can cause issues

You should never redesign your experiment. try and see what in your experiment you made a mistake on or try and test your experimemt with somebody else. see if they get the right results.