Answer: Although
Step-by-step explanation:
In grammar, the role of conjunction is to link different elements including words, ideas, or even clauses. This implies they act as a connector and often indicate the relationship between the elements they link. Examples of these words include: and, however, until, so, among others.
In the sentence presented, the conjunction is "although" because this word serves as a connection and transition between the clauses "my sister likes chips" and "although I like popcorn the best" by showing contrast. Also, this is a subordinating conjunction, which is the type of conjunction that joins elements in a complex sentence like the one presented (dependent and independent clause sentence).