The correct matches are:
1. obsidian - B) extrusive igneous;
2. granite - A) intrusive igneous;
3. conglomerate - C) clastic sedimentary;
4. evaporite - E) chemical sedimentary;
5. coal - D) organic sedimentary;
6. marble - F) metamorphic;
There are three big groups of rocks, igneous, sedimentary, and metamorphic. They further diversify into multiple types of rocks in accordance to their structure, chemical composition, crystallization, formation etc. The igneous can simple be divided into intrusive (ones that formed on the surface or very close to it) and extrusive (ones that formed deep into the ground). The sedimentary rocks can be divided into multiple groups in accordance to their composition, as some can be made of multiple sediments, some from organic material, some from mixture of sediments and organic material etc. And the metamorphic can simply be seen as rocks that come to be as a result of the transformation of the other two types if they are under big pressure and temperatures for longer periods of time.
