What is a characteristic of metamorphic rock?

Metamorphic rocks are characterized by their formation process, which involves significant changes due to extreme heat and pressure. This transformation occurs when pre-existing rocks, which can be igneous, sedimentary, or even other metamorphic rocks, are subjected to conditions deep within the Earth. The intense heat can cause the minerals in these rocks to recrystallize, while pressure can lead to the alignment of minerals, giving metamorphic rocks their distinct textures and structures, such as foliation.

In contrast, the other options refer to different geological processes. The formation of rocks from lava cooling describes igneous rocks, while the presence of fossils is a typical feature of sedimentary rocks, which form from the accumulation and compaction of sediments. Lastly, the layering of sediments is also indicative of sedimentary rock formation, not metamorphic. Thus, option A accurately encapsulates the defining characteristic of metamorphic rocks.