A comma splice is a term used when a comma is used to separate two independent clauses. Even though we don't have the original sentence that shows the comma splice, we can still read the sentences to figure out which sentence is correct.
In this case, the correct sentence is, "Crafts once fulfilled useful purposes, but now crafts are used mainly for decoration" (B).
We have two separate ideas:
- Crafts once fulfilled useful purposes.
- Now crafts are used mainly for decoration.
In order to connect these two separate ideas with a comma, we need to add the appropriate transition word, like but. Note, that letter C is not correct because no comma is used. Letter D is not correct because the transition word, even now, doesn't make sense in the context of the sentence since the two uses are different.