Question

Which sentence is punctuated correctly?

The aliens suffered from exhaustion, after traveling several light years.
They needed some relaxation, when they finally landed their spaceship.
After they rested a few days, the aliens revived sufficiently to explore.
They needed all their energy, once they started hiking the rough terrain

Answer 1

The correctly-punctuated sentence is: "After they rested a few days, the aliens revived sufficiently to explore."

According to English grammar, when you have a sentence with an adverbial dependent clause which comes before the independent clause, you should add a comma before the independent clause.

Here, the adverbial dependent clause is "After they rested a few days:"

• dependent because it does not express a full thought and cannot stand on its own as a sentence,
• adverbial because it starts with the subordinating cunjunction after, thus giving an information about the main verb of the sentence (rested).