In retail, they say the customer is always right, and that applies to engineering to a degree. Civil engineers will no doubt cross paths with difficult clients throughout their career and will have to find a way to grit their teeth and get through it. A client may be too demanding or lacking in communication skills. It's up to you as the engineer to navigate your clients' whims and moods to prove to them that your firm has what it takes to get the job done. Highlight an experience you had with a difficult client and how you were able to make the relationship work and complete the job successfully.