Answer:
The answer is: a. It tries to convince children to support Communism against its enemies.
Step-by-step explanation:
A "propaganda" is a type of information that is meant in order to achieve a cause. Most of the time, such cause is political in nature. This tries to manipulate people by using banners, words, songs, displays, symbols, etc.
In the song above, it is clear that it is a propaganda trying to convince children to support "Communism" against its enemies. Children are very easy to manipulate thus, allowing them to sing to a song's lyrics allows them to connect their body and mind. It also aids in their imagination. So, if they are to sing this song every day, they will then be convinced gradually that Communism is good.
Thus, this explains the answer.