Answer:
This is an example of adjective clause
Explanation:
The term which is used in the example and Adjective Clauses inform me that a noun is included in the example, which ends up supporting my answer because the noun occurs at a certain time (which transitions the fact that Diwali, a Hindu festival is celebrated on autumn.)
The answer is c because it connects the sentence
<span>The Ghost was definitely not reliable. </span>