(A) ** Greece and Bulgaria
(B) Bulgaria and Italy
(C) Bulgaria and Corfu
(D) Bulgaria and Germany
EXPLANATIONS BELOW
Concept note-1: -The Incident at Petrich, or War of the Stray Dog, was a Greek–Bulgarian crisis in 1925 that resulted in a brief invasion of Bulgaria by Greece near the border town of Petrich after the killing of a Greek captain and a sentry by Bulgarian soldiers. Demir Kapia, where the original incident took place.
Concept note-2: -The Second Balkan War was a conflict which broke out when Bulgaria, dissatisfied with its share of the spoils of the First Balkan War, attacked its former allies, Serbia and Greece, on 16 (O.S.) / 29 (N.S.) June 1913. Serbian and Greek armies repulsed the Bulgarian offensive and counter-attacked, entering Bulgaria.
Concept note-3: -Due to the strong political, cultural and religious ties between the two nations, (the majority of Bulgarians and Greeks practice the Eastern Orthodox faith), Bulgaria and Greece today enjoy excellent diplomatic relations and consider each other a friendly nation and an ally.
Concept note-4: -At 475 km in length, the border between Bulgaria and Greece begins in the west at the tripoint between the borders of Bulgaria, Greece and Macedonia.