Context: Read the text.
Igneous rock forms when melted rock, like magma or lava, cools and hardens. The faster the rock cools, the finer its grain. That's because there isn't as much time for crystals to form. A rock like obsidian cools quickly and creates a smooth and glassy black rock. Obsidian can be chipped down into a fine point. Granite, on the other hand, cools slowly. It has large mineral grains that form as it cools. The grains create interesting patterns, which is why granite is often used for kitchen countertops.
Which term matches the picture?
A. obsidian
B. granite
Determine the correct option from the provided choices and reply with its corresponding letter.

B