An example of a secondary source is:
a. an encyclopedia article
b. an autobiography
c. a census report
d. a diary

A

Explanation:

I believe the answer is A, since an encyclopedia article is not coming directly from a person, unlike a diary, which is a primary source.

the correct answer is 4) heat and pressure

metamorphic rocks arise from transformation of existing rocks types, in a process called metamorphism. during metamorphism the original rock(prolith) change into metamorphic rock by heating (150-200c) and pressure of more than 1000 bar. the original rock can be sedimentary, igneous, or existing metamorphic rock.