题目

如图，直线y=x+2与两坐标轴交于A、B两点，将x轴沿AB翻折交双曲线y=（x＜0）于点C，若BC⊥AB，则k=       。 答案：-4We _____________ the library on foot. [     ]A. am going toB. is going toC. are going to