Answer:
Large
Step-by-step explanation:
When magma cools slowly they have large structure. It is so because the crystals get sufficient time to grow large. And magma which cools quickly do not get sufficient time to grow large
Basically the magma which cools slowly, cools below the ground. And the magma which cools quickly, cools above the ground.
During cooling process molten rocks consolidate and form mineral crystals whose size depends on the time taken for cooling.