C The results are suggestive of a true treatment effect, but the study has limited power to detect the effect due to the relatively small number of study subjects
While the p-value for the differences between the mean days of post-operative hospitalization is not below the conventional level of 0.05, it is relatively close to that value. The values of the treatment group and placebo group means (3.0 and 4.5 days, respectively) do suggest that there is an effect of treatment. It is likely that the statistical power of the study is rather limited, given the modest number of people enrolled in each group. Ideally, this study would be repeated with larger numbers of study subjects in each of the two groups. While it would be a mistake to conclude that there was definitively a treatment effect, it would also be a mistake to conclude that there was no evidence for a treatment effect, as well.
In clinical trials, it is not necessary that the comparison groups have identical numbers of subjects, although there should be a sufficient number of participants in each study group to effectively evaluate the treatment being considered. While statistical testing of two group means may use the t-test, it possible to derive a p-value from the use of this test.