How does the divergent boundary in Ireland produce the islands around the country's waters?

a
The underwater plates move apart from each other, causing an upwelling of lava that immediately cooled in the water, producing the islands
b
The underwater plates moved towards each other, crashing and causing an explosion of lava, that immediately cooled into islands dotted around the waters
c
The underwater plate subducted under the land plate, causing the land plate to break off a piece, which traveled into the ocean becoming an island
d
Two underwater plates move collide with each other, pushing their edges up, with the tips coming out of the water, making the islands

c

The underwater plate subducted under the land plate, causing the land plate to break off a piece, which traveled into the ocean becoming an island.