In the diagram:

R2 and R4 areboth within AS 65540, which indicates that they are in thesame Autonomous System.

eBGP (External Border Gateway Protocol)is designed for routingbetween different ASes(inter-AS routing).

Since R2 and R4 are in thesame AS, you would use:

OSPForIS-IS(both interior gateway protocols – IGPs)✔

Static routingis also valid between any two routers if manually configured✔

eBGP❌is invalid between routersin the same AS.

➡The correct protocol in that case would beiBGP (internal BGP)if BGP were to be used within the AS.

Therefore, the correct answer is: D. eBGP