When comparing survival times between two groups, why can't we use the two-sample t-test? I. because some of the survival times may be censored II. because survival time may not have a normal distribution III. because survival time often needs to be weighted IV. because survival time doesn't have a known standard deviation

Group of answer choices

a. I, II, III and IV

b. I and II only

c. I only

d. I, II and III only