Assertion: The Communist Party of India supported the decision of Congress to impose an emergency in 1975.
Reason: It believed that there was an international conspiracy against the unity of India and in such circumstances some restrictions on agitations were justified.

Both the Assertion and the Reason are correct and the Reason is the correct explanation of the Assertion.

Some other parties, like the CPI that continued to back Congress during the Emergency, also believed that there was an international conspiracy against the unity of India. It believed that in such circumstances some restrictions on agitations were justified.