Passage 2 阅读理解32. Field testing in America has shown that ___________.

A、non-GMcropsaremoreenvironment-friendlythanGMcrops;
B、concernsoverthethreatsofGMcropsareexaggerated;
C、GMcropsposeseriousthreatstobiodiversity;
D、cross-pollinationhasintroducednastyspeciesintothehumanfoodchain