Here's why:
* Adverb clauses modify verbs, adjectives, or other adverbs. They answer questions like "how," "when," "where," "why," or "to what extent." They usually begin with subordinating conjunctions like "because," "although," "since," "when," etc.
* Adjective clauses modify nouns or pronouns. They answer questions like "which one?" or "what kind?" They usually begin with relative pronouns like "who," "whom," "whose," "which," or "that."
The phrase "you passed" doesn't have any of the characteristics of either clause type. It's simply a verb phrase containing a pronoun ("you") and a past tense verb ("passed").
To make a clause out of "you passed," you would need to add more information. For example:
* Adverb clause: "You passed because you studied hard." (The clause "because you studied hard" modifies the verb "passed" and tells us why the action happened.)
* Adjective clause: "You passed the test that was very difficult." (The clause "that was very difficult" modifies the noun "test" and tells us which test the person passed.)