SC - China
B is best
During + time period is correct usage
During the 1970's and the 1980's
We need a specific time frame following "During".
We dont know which two decades??..
A is out...
E ... We need "was" instead of " is".
D.... Being ...a big no-no
C...i feel its does not convey the idea of the "past tense" required in the first half of the sentence