Here's why:
* Correlative conjunctions always come in pairs and connect words or phrases that have equal grammatical weight.
* "Either...or" is a classic example of a correlative conjunction. It's used to present two options, indicating that one or the other is true.
Let's look at the other options:
* A - since: This is a subordinating conjunction, introducing a dependent clause.
* B - and: This is a coordinating conjunction, but not correlative.
* D - because: This is a subordinating conjunction, introducing a dependent clause.
Example:
* Either you can go to the movies or stay home and watch TV.