What is the primary purpose of randomization?

A) To prevent bias in the assignment of treatment
B) To provide a probability basis for statistical testing
C) To ensure the same number of people are randomized to each group
D) To ensure that the subjects not to know which group they are assigned to
E) To guarantee the comparability of the different treatment groups

The primary purpose of randomization is to reduce the bias from investigator to assign the treatment to participants."To provide a probability basis for statistical testing" is not correct.Probability basics are not related with randomization."To ensure the same number of people are randomized to each group" is not correct.The same number of people to each group can be guaranteed by other ways such as exclusion or dropping participants."To ensure that the subjects not to know which group they are assigned to" is not correct and this is a description of blinding (masking)."To guarantee the comparability of the different treatment groups" is not correct.Even though randomization increases the comparability of different treatment group,it cannot guarantee the comparability and it is not the primary purpose of randomization.