metamorphic rocks: are formed when igneous or sedimentary rocks are subjected to extreme heat 
(metamorphic rocks; are formed; T:when igneous or sedimentary rocks are subjected to extreme heat) (igneous or sedimentary rocks; are subjected; to extreme heat)
metamorphic rocks igneous or sedimentary rocks
are formed are subjected
T:when igneous or sedimentary rocks are subjected to extreme heat
to extreme heat