The correct answer is C. checked.
Censorship is the suppression of information that may be considered objectionable or harmful. It is often used by governments to control what information is available to their citizens. During times of war, governments may censor mail in order to prevent the spread of information that could be harmful to the war effort. This could include information about troop movements, military plans, or other sensitive information.
The other options are incorrect because they do not accurately describe the process of censorship. Option A, distributed, is incorrect because censorship does not involve the distribution of mail. Option B, confiscated, is incorrect because censorship does not involve the seizure of mail. Option D, supervised, is incorrect because censorship does not involve the monitoring of mail.
In conclusion, the correct answer is C. checked.