Step 1: Understand the selection process.
The selection of executives is a process that applies to all levels of management, from lower to top-level executives. The process is based on the skills and qualifications needed for each role.
Step 2: Evaluate the options.
- Selection of lower, middle, and top-level executives is all part of the organizational hierarchy.
- Each level of executive requires specific qualifications and skills suited for the responsibilities of that role.
Step 3: Conclude.
The selection of executives involves all levels of management, depending on the needs of the organization.
Final Answer:
\[
\boxed{\text{All of these}}
\]