题干
Over the years the European Union has made great efforts to _______ the safety of food and protect the health of its people.
A：discover
B：ensure
C：revise
D：react
答案(点此获取答案解析）
B
的两根分别为一个椭圆和一个双曲线的离心率，则
的取值范围是（ w.w.*w.k.&s.5*u.c.om）
