“Because you're mine, I walk the line.”
which clause

There is a subordinate clause: “Because you're mine,".

There is an independent clause: "I walk the line.”

Explanation:

The subordinate or dependent clause is the part of the sentence that depends on the main clause to form a complete sentence.  It is often introduced by a conjunction.  The subordinate clauses can be noun, adverb, or adjective clauses.  The independent or main clause is the part of the sentence that contains the subject and the verb and can stand on itself as a meaningful sentence.

i think it could possibly be b

i think its a.

an ugly duckling is teased by the other ducklings. when she grows up, however, the ducklings discover that she is a beautiful swan