In Evaluating Mortality Rates,the Head Nurse on the Cardiac Unit

In evaluating mortality rates,the head nurse on the cardiac unit is surprised to find that they are higher on the weekend than on weekdays.In exploring the reasons for this apparent anomaly,the head nurse focuses on

A) availability of diagnostic personnel.
B) availability of physicians.
C) communication with on-call providers.
D) numbers of acutely ill patients.