Analyze the sentence to determine the main clause and the subordinate clause. then choose the function of the subordinate clause.

the mason-dixon line, which is perhaps the most famous border ever established by surveying methods, has been designated a national historic civil engineering landmark.

1.main clause:
a. the mason-dixon line
b. the mason-dixon line, which is perhaps the most famous border ever established by surveying methods
c. the mason-dixon line has been designated a national historic civil engineering landmark
d. the most famous border ever established by surveying methods has been designated a national historic civil engineering landmark
e. has been designated a national historic civil engineering landmark

2.subordinate clause:
a. which is perhaps the most famous border ever established by surveying methods has been designated a national historic civil engineering landmark
b. has been designated a national historic civil engineering landmark
c. which is perhaps the most famous border ever established by surveying methods

3.subordinate clause functions as a(n):
a. adjective
b. adverb
c. noun

To answer this question, researchers studied populations of the dusky salamander (desmognathus ochrophaeus) living on different mountain ranges in the southern appalachian mountains. the researchers tested the reproductive isolation of pairs of salamander populations by leaving one male and one female together and later checking the females for the presence of sperm. four mating combinations were tested for each pair of populations (a and b)—two within the same population (female a with male a and female b with male b) and two between populations (female a with male b and female b with male a). the proportion of successful matings for each mating combination was measured. for example, when all the matings of a particular combination were successful, the researchers gave it a value of 1; when none of the matings were successful, they gave it a value of 0. then the researchers calculated an index of reproductive isolation that ranged from 0 (no isolation) to 2 (full isolation). the reproductive isolation value for two populations is the sum of the proportion of successful matings of each type within populations (aa + bb) minus the sum of the proportion of successful matings of each type between populations (ab + ba). the table provides data for the geographic distances and reproductive isolation values for 27 pairs of dusky salamander populations.