题目

You can hardly imagine the difficulty the woman had______her children. A.brought up       B.to bring up  C.bringing up      D.to have brought up   答案：C本题考查have difficulty(in) doing sth.这一结构。本句中 the woman had为定语从句,修饰difficulty。过抛物线y=2x2的焦点的直线与抛物线交于A(x1,y1),B(x2,y2),则x1x2=(　　)(A)-2 (B)- (C)-4 (D)-