"Because I love you."
Translation:Parce que je t'aime.
Konstructiv's link above applies to your question too, although for slightly different reasons. Here's the explanation from the Duolingo link provided by Konstructiv:
"Parce que, car, and puisque all mean "because" and describe some kind of cause-and-effect relationship, but they aren't completely interchangeable.
Parce que is a subordinating conjunction that provides an explanation, motive, or justification.
- Elle lit parce qu'elle a un livre. — She is reading because she has a book.
- Parce qu'elle est jeune, elle est jolie. — She is pretty because she is young.
Car is similar to parce que, but it's a coordinating conjunction and thus cannot begin a sentence or clause.
- Je mange du poulet, car j'aime la viande. — I am eating chicken because I like meat.
Puisque is a subordinating conjunction that means "because" or "since" and gives an already-known or obvious reason or justification."
- Puisque il pleut, j'ai un parapluie. — Since it's raining, I have an umbrella.