（190）GWD-17-Q31
The agreement, the first to formally require industrialized countries to cut emissions of gases linked to global warming, is a formal protocol by which 38 industrialized countries must reduce emissions of these gases by 2012 or face heavy penalties.

A.by which
B.for which
C.under which
D.such that
E.wherein

弱弱的问一下，这个答案的under，应该放道后面句子的哪里？