Answer: 4. I wanted to go to the concert; however, I realized I didn't have enough money.
Explanation: A semicolon is used to separate two independent clauses that are closely related in meaning. In this sentence, "I wanted to go to the concert" and "I realized I didn't have enough money" are two independent clauses that are related in meaning. The semicolon is used to separate them instead of a comma because they are two complete thoughts that could stand alone as separate sentences.