A common cold is caused by a virus, not bacteria
To have an accurate result for this experiment, it is best for the scientist to be able to find or devise an appropriate methodology coupled with the most accurate tools or equipment. When data are properly gathered, it is easier for the scientist to interpret and give conclusion/recommendations.
DNA replication needs to occur because existing cells divide to produce new ones . It needs to be copied before cell division so each new cell created can receive a new full set of “instructions”