Answer:
a and c
Explanation:
Basalt pillows occur when the basalt flows into the sea and the hot lava's contact with the cold sea water, the thermal shock, shapes the basalta into a rounded (pillow-like) shape, cooling the surface while a mass of Basalt is kept inside. For this reason, we can say that basalt pillows are an underwater shape, characterized as lens-shaped masses surrounded by cooled shells.
