Final answer:
The best way to punctuate the sentence is with a semicolon.
Step-by-step explanation:
The answer that best punctuates the sentence for clarity is:
There was only one thing to do; study till dawn.
Punctuating the sentence with a semicolon (;) helps to clearly separate the two independent clauses and show the relationship between them. This makes the meaning of the sentence easier to understand.
Learn more about Punctuation in English sentences