Red meat and heart disease. A study presented at ESC Preventive Cardiology 2021, an online scientific congress of the European Society of Cardiology (ESC), explored the link between red meat consumption and heart disease. The study included 19,408 participants of the UK Biobank and examined associations of self-reported intake of red meat with heart anatomy and function using three methods: first, cardiovascular magnetic resonance (CMR) assessments of heart function used in clinical practice such as volume of the ventricles and measures of the pumping function of the ventricles; second, novel CMR radiomics used in research to extract information from heart images such as shape and texture (which indicates health of the heart muscle); third, elasticity of the blood vessels (stretchy arteries are healthier). For this study, identify each of the following:

a. Experimental unit

b. Response variable

c. Factor

d. Factor levels