The sentences that use a semicolon incorrectly are:
- Inside the cottage, the detectives found fingerprints on a plastic cup; which they considered an important clue to the mystery.
- If you take the bus downtown; I will meet you on the first floor of the library by the elevators; the ones to the right as you enter the building.
- The study of a foreign language covers several areas; the history of the language, the literature written in the language, and the culture of the people who speak the language.
The second sentence contains two incorrect uses of the semicolon, while the first and third sentences each contain one incorrect use. The first sentence incorrectly uses a semicolon before a dependent clause, while the second incorrectly uses a semicolon to separate independent clauses and the third incorrectly uses it to separate items in a list.