Job analysis is the correct answer. Job analysis is a systematic process of gathering and analyzing information about the duties, responsibilities, tasks, and requirements of a particular job. It focuses on job content, environment, and conditions of employment.

Job description:
- A job description is a written statement that outlines the specific duties, responsibilities, and requirements of a particular job. It provides information about the tasks to be performed, the qualifications needed, and the reporting relationships.
- While a job description may include information about job content, it does not typically focus on the environment and conditions of employment.

Human resource inventory report:
- A human resource inventory report is a document that provides an overview of the skills, qualifications, and experiences of the employees in an organization.
- It typically includes information such as employee names, job titles, education, training, and previous work experience.
- While this report may provide some information about employees' job content, it does not specifically focus on the environment and conditions of employment.

None of the given options:
- This option is not correct because one of the given options, job analysis, does focus on job content, environment, and conditions of employment.

Conclusion:
- Job analysis is the process of gathering and analyzing information about a job's duties, responsibilities, tasks, and requirements.
- It focuses on job content, environment, and conditions of employment.
- Job descriptions provide information about specific job duties and requirements but do not typically focus on the environment and conditions of employment.
- Human resource inventory reports provide an overview of employee skills and qualifications but do not specifically focus on the job content, environment, and conditions of employment.