Answer: Maintenance engineer
Step-by-step explanation:
Design engineer is an engineer that uses both mathematical and scientific methods to develop ideas that will be used and design that'll be used for a particular product.
Inspection engineers are the engineers that checks out roads, bridges etc and identify problems that such structures have so as to prevent accidents from happening.
Technical sales engineer advices the company and also give support with regards to products when technical expertise may be required.
Maintenance engineers are the engineers that are involved in checking, and servicing equipments and machinery and making sure that they're always functioning properly and in good, working conditions. These engineers ensures the smooth running of machines.
Based on the above scenario, the answer is maintenance engineers.