Final answer:
Sentences c) and d) use semicolons incorrectly because they fail to connect two independent clauses. Semicolons should connect independent clauses or clarify lists with internal commas, not separate dependent clauses from independent clauses or replace commas in complex lists.
Step-by-step explanation:
The sentences that use semicolons incorrectly are:
- c) Alicia cast Sean in the supporting role; though she preferred Harold for the part. This is incorrect because 'though she preferred Harold for the part' is not an independent clause that can stand on its own.
- d) Harboring doubts that his script had energy and cleverness; Charles wasn’t sure the actors would like their parts. Here, a semicolon is used incorrectly to separate a dependent clause from an independent clause.
To provide further clarification, semicolons should be used to connect two independent clauses, particularly when the second clause restates the first or when the two clauses are very closely related. Semicolons can also be used for lists where the elements contain commas to improve clarity. However, they should not be used to separate dependent clauses from independent clauses or to replace commas in lists with multiple items. Using semicolons correctly can help prevent comma splices and clarify the relationship between clauses.