Answer:
Its message is unreliable because it is an example of pro-communist propaganda
Step-by-step explanation:
The message in the poster shows some soldiers pointing to another soldier that caught someone with the flag of the United States with the inscription, "Long live the victory of the Korean People's Army and the Chinese People's Volunteer's Army" which is a pro-communist message and as such it is reliable because the United States is an anti-Communist and pro-Capitalist state.
The statement that best describes the reliability of this poster as a primary source is because its message is unreliable because it is an example of pro-communist propaganda