Enzyme activity is affected by ph because .

 change the shape of the active site of an enzyme

Explanation:

Enzymes are also sensitive to pH . Changing the pH of its surroundings will also change the shape of the active site of an enzyme. ... This contributes to the folding of the enzyme molecule, its shape, and the shape of the active site. Changing the pH will affect the charges on the amino acid molecules.

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.