Before reporting the results of the survival analysis, the investigators compared baseline characteristics of the 38 people who withdrew from the study before its end to those who had complete follow up. this was done for which of the following reason?a. To test whether randomization was successful
b. To check for changes in prognosis over time
c. To check whether those who remained in the study represent the total study population
d. To determine whether the outcome of those who remained in the study is the same as the outcome of the underlying population
e. To check for confounders in the exposed and nonexposed groups