Answer the following question given this paragraph: 

Coal has different grades. Bituminous coal forms at lower temperatures. It contains a lot of sulfur. When it is burned, it causes a lot of pollution. Anthracite coal forms under higher temperatures. This drives off the sulfur, and the coal burns more cleanly.


Q: What type of coal is formed at lower temperatures?

 Choices:

- clean

- calcareous

- limestones

- bituminous

A:
bituminous
