Choice "A" is correct. Worker's compensation benefits are available if the employee is injured within the scope of employment.
Choice "b" is incorrect. The injury need not occur on workplace premises; it need only occur within the scope of employment. Thus, if an employee is injured off-site but while working for an employer, the employee is covered.
Choice "c" is incorrect. This choice is wrong for two reasons: worker's compensation covers only employees ("agent" is broader) and, in most cases, commuting to and from work is not within the scope of employment.
Choice "d" is incorrect. This choice also is wrong for two reasons: again, not all agents are employees and so not all agents are covered, and use of one's automobile for personal purposes is not within the scope of employment.