题目

若向量与向量共线，则（ ）A. 0 B. 4 C. D. 答案：【答案】D【解析】因为与向量共线，所以，解得， ，故选D.A beam of light will not bend round corners unless______to do so with the help of a reflecting device.A.having been madeB.being madeC.madeD.you make