题目

如图所示，正方形ABCD和正方形ABEF交于AB，M、N分别是BD、AE上的点，且AN=DM. 试用向量证明∥平面EBC.   答案：证明：设=a, =b,=c,因为=λ1(c+b), =λ1(c-a), =a+λ1(c-a)=(1-λ1)a+λ1c，所以=-=（λ1-1）a+λ1b.依共面向量定理知，与a,b共面，∴MN∥平面EBC，即∥平面EBC. The twins are coming to Meirmei’s house tonight．She will give them ________ to eat． [　　] A．anything delicious B．something Chinese C．Chinese something D．delicious anything