Discussed many a times , one of the thread below:sc-science-of-economics-43497.html
The science of economics, which for four decades was
dominated by Keynesians, who at first stressed
the government’s role in stimulating the economy, but who were ultimately led away
from solutions based on government intervention.
(A) economics, which for four decades was
(B) economics that was to be
(C) economics, one which has, for four decades, been
(D) economics is one that for four decades has been
(E) economics, for four decades, is one that was
Doesn't the text in bold suggest that the Keynesians no longer dominate the economics. So we don't need a present continuous tense as in D.