Each statement in a dichotmous key has only 2 choices and they should be

x would be the most and the least would be y because there are more fruit   and seeds than flock z has insects

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.

answer; ///(a) ;