To show he presence of a trait you would need to follow it through multiple generations in a pedigree.
Variables is likely the correct answer.
Answer:
Examples of environmental factors that may alter salivary peroxidase include periodontitis, oral hygiene, presence of heavy metal ions, bacteria (e.g., <em>Streptococcus gordonii</em>), anaerobic conditions, temperature, pH, etc.
Explanation:
Peroxidase is an enzyme found in all aerobic cells that act to convert toxic hydrogen peroxide (H2O2) into dioxygen (O2) and water (H2O). This enzyme plays an important non-specific defensive role against proliferating micro-organisms that cause periodontal diseases such as periodontitis, which is a serious inflammatory disease affecting the tissues around the teeth. The most common environmental factors influencing the development of periodontitis include oral hygiene, smoking and age. In this regard, it has recently been shown that there is a positive correlation between salivary peroxidase activity and periodontal health, especially in non-smoker individuals. In consequence, it is expected that smoker individuals are more prone to suffer periodontal diseases by reduction of the salivary peroxidase levels.
The answer is either C because both C and D cause disease, but only C is a living organism. Hope that helps!
