Answer:
Ridicule is used to show the gullibility of the Russian citizens.
Step-by-step explanation:
It is not "personification is used to show the reader Stalin's thoughts and feelings" because the thoughts are Clover's, who, in this allegory does not represent Stalin.
It is not "parody is used to illustrate the impact of Stalin's purge, because the question asks for the use of "satire". The definition of satire is the use of humor, irony, exaggeration, or ridicule to expose and criticize people's [lack of intelligence] or vices, particularly in the context of contemporary politics and other topical issues. Thus, even though Animal Farm is an allegory to the Russian situation and this paragraph refers to Stalin's purge, satire is not used to support this allegory (or, not by parody at least).
Excellent. Thus it must be "ridicule is used to show the gullibility of the Russian citizens". This is the correct answer. Recall the definition of satire: it includes the words "ridicule" and "criticize people's [lack of intelligence]". This fits perfectly with the author using ridicule to show the gullibility, or one representation of a lack of intelligence, with the Russian citizens.
Hope this helps!