Step 1: Understanding work
- Work is generally defined as any activity or effort performed to achieve a goal or result.
- It can include physical, mental, or emotional effort and can be part of any task or response to stimuli.
Step 2: Analyzing options
- (A) Activity: While work is often linked to activity, it is not limited to just physical activity.
- (B) Response: Work can also be a response to a stimulus, making this option partially correct.
- (C) Effort: Work certainly involves effort, but the definition is broader than just effort.
- (D) All of these: Since work encompasses activity, response, and effort, this is the most accurate definition.
Step 3: Conclusion
Thus, the correct answer is (D) All of these since work is not limited to one of the components but involves all aspects.
\[
\boxed{\text{Correct Answer: (D) All of these}}
\]