Read the following sentences:
We couldn't get into the house. The front and back doors were locked.
Which revision uses a subordinating conjunction and correct punctuation?
O Because the front and back doors were locked, we couldn't get into the house.
We couldn't get into the house, since the front and back doors were locked.
O The front and back doors were locked, so we couldn't get into the house.
We couldn't get into the house, for the front and back doors were locked.