**Core Concept**
Randomized Controlled Trials (RCTs) are a gold standard in clinical research for evaluating the efficacy and safety of interventions. An RCT involves randomly allocating participants to either an experimental group or a control group, allowing for a comparison of outcomes between the two groups.

**Why the Correct Answer is Right**
In an RCT, dropouts or withdrawals are not typically excluded from the study. Instead, they are usually analyzed as part of the intention-to-treat (ITT) principle, which involves analyzing all participants according to the group they were originally assigned to, regardless of whether they completed the study or not. This approach helps to minimize bias and provide a more accurate representation of the study's results. The ITT principle is particularly useful in RCTs because it can help to account for any differences in outcomes between those who completed the study and those who did not.

**Why Each Wrong Option is Incorrect**
**Option A:** Baseline characteristics being comparable is a key feature of RCTs, as it helps to ensure that the groups being compared are similar in terms of relevant factors. This is achieved through the randomization process, which aims to distribute both known and unknown confounding variables evenly between the groups.
**Option C:** The sample size of an RCT does indeed depend on the type of study, among other factors such as the expected effect size, the level of precision required, and the anticipated dropout rate. A larger sample size may be needed for studies with smaller expected effect sizes or higher dropout rates.
**Option D:** Double blinding can help to reduce bias in RCTs by preventing both the participants and the researchers from knowing which group each participant is in. However, it is not a foolproof method for eliminating bias entirely, as other sources of bias such as selection bias or information bias may still occur.

**Clinical Pearl / High-Yield Fact**
In RCTs, the ITT principle is often used to analyze data from dropouts, which can help to provide a more accurate representation of the study's results. This is particularly important in studies with high dropout rates, as it can help to minimize bias and ensure that the results are generalizable to the target population.

**✓ Correct Answer: B. Dropouts are excluded from the study**