Final Answer:
Allows an employee to quit a job whenever they want to, unless there is a contract in place that specifies their length of employment or conditions for leaving employment is known as at-will employment (Option B).
Step-by-step explanation:
At-will employment is a principle in employment relationships that allows either the employer or the employee to terminate the employment relationship at any time, for any reason, as long as there is no contractual agreement specifying otherwise. Option A (Employment flexibility) is a broad term that may encompass various employment arrangements, including at-will employment.
Option C (Contractual employment) implies a specific employment contract, and Option D (Job security) suggests a more stable and secure employment situation, which is contrary to the concept of at-will employment.
Option B is the answer.