设f(x,y)=x3-y3+3x2+3y2-9x,则f(x,y)在点(1,0)处().
A.取得极大值
B.取得极小值
C.未取得极值
D.是否取得极值无法判定
参考答案:B
Everyone of us _____ it’s important _____a seat belt in the car.
A.knows, wears
B.know, to wear
C.knows, to wear
D.know, wearing
为什么甘蔗的下段比上段甜?