Both options b and c are the same. However, they are not correct.
Answer:
d. As long as you observe the ethics guidelines in your company's employee handbook, you have nothing to fear from your next employee performance appraisal.
Explanation:
Complex sentences such as this one, with an independent clause and a subordinate clause, cannot be separated by semicolon or colon - they must be separated by a comma. Instead, a semicolon and colon can be used to divide two independent clauses in a compound sentence, which can stand on their own separately.