Final answer:
The sentence that is punctuated correctly is option b.
Step-by-step explanation:
The sentence that is punctuated correctly is option b. The correct punctuation in this sentence is the semicolon (;) which is used to separate two independent clauses. In the sentence, 'I thought the promotion was mine; however, my attendance wasn't good enough,' the semicolon is used to connect the two related thoughts while indicating a stronger pause compared to a comma.
Options a, c, and d contain punctuation errors. Option e is a run-on sentence, as it is missing appropriate punctuation to separate the two independent clauses. Therefore, only option b is punctuated correctly.
Learn more about Punctuation in English sentences