What does serology examine in relation to pathogens?

Serology specifically focuses on the examination of antibodies in the blood serum that are produced in response to pathogens, such as viruses or bacteria. This testing allows for the detection of specific antibodies that indicate whether an individual has been exposed to a particular pathogen or if they have mounted an immune response to it. The presence of these antibodies can provide valuable information regarding past infections and the current immune status of the individual.

In contrast, the other options do not accurately represent the focus of serology. Investigating DNA sequences characteristic of pathogens pertains more to molecular techniques like PCR rather than serology. Measuring the amount of bacteria on a surface relates to microbial load assessments, which are different from antibody detection. Analyzing surface proteins of a pathogen may involve techniques such as proteomics or immunohistochemistry, but does not specifically pertain to antibody examination or serological testing. Therefore, the primary goal of serology is the evaluation of antibodies against a pathogen, making this the correct answer.