Which of the following variable pairs could be summarised using a contingency table. Question 1Answer a. A treatment variable (control or treatment) and a binary variable of whether patient became sick (healthy or sick) b. A treatment variable (control or treatment) and length of illness (measured in days sick) c. A treatment variable (control or treatment) and average heart rate (measured in beats per minute). d. Blood vitamin levels (measured in milligrams per litre) and blood glucose levels (measured in mmol/L)