Which of the following statements about employer drug testing is true?

An employer's ability to conduct drug testing is often influenced by legal regulations and workplace policies. The option that states an employer can conduct a drug test on employees involved in an accident is indeed accurate and represents a common practice in many workplaces. This type of testing is generally considered a standard safety measure to ensure a safe working environment and to assess the cause of the incident.

On the other hand, the statement that an employer can only test with the employee's permission is also correct, as many jurisdictions require consent for drug testing, especially in non-safety-sensitive roles. Combining both of these accurate statements reflects a comprehensive understanding of drug testing policies, which is why this choice is the most accurate among the ones presented.

Random drug testing for any reason is often restricted by laws and regulations and does not generally hold true, and while permission is often required, the emphasis on the necessity of testing after an accident adds depth to the correct answer, since it highlights specific legal and practical considerations involved in workplace drug testing.