Step 1: Understanding the sentence.
The sentence implies that the person’s salary matches or aligns with the amount of work done. The word needed should express this alignment or conformity. "Keeping" fits as it indicates conformity or alignment with something else.
Step 2: Analyzing other options.
- Accord refers to an agreement, but does not fit the context of salary and work alignment.
- Coordination refers to working together in an organized way, which doesn't make sense in this context.
- Balance refers to an equilibrium, but it does not directly suggest the relationship between salary and work done.
Step 3: Conclusion.
"Keeping" is the most suitable word here, meaning that the salary is aligned or in harmony with the amount of work done.
Thus, the correct answer is 4. keeping.
Final Answer:
\[
\boxed{\text{The correct answer is 4. keeping.}}
\]