Final answer:
Gerald's social superiority both enhances and strains his relationship with Mr. Birling in 'An Inspector Calls' as Birling seeks to gain status through the match yet also feels the need to prove himself to Gerald.
Step-by-step explanation:
In J.B. Priestley's play An Inspector Calls, the character Gerald Croft is indeed of a higher social status than Mr. Birling, primarily because Gerald's family business is bigger and more influential than that of the Birlings. This social superiority has a multidimensional impact; we could argue that it both enhances their relationship and strains it. Initially, Mr. Birling is keen to impress Gerald and is pleased about the possibility of his daughter marrying into a higher social standing. This suggests Gerald's social superiority enhances the relationship by aligning with Mr. Birling's aspirations for status and recognition.
However, there is also an underlying tension because Mr. Birling is aware of Gerald's superior status, which makes him somewhat subservient or eager to prove himself, thereby straining their relationship. This is more subtly conveyed through their interactions and Mr. Birling's sometimes overzealous demeanor toward Gerald. Therefore, the correct answer could be argued as d) Both a and b.