则可以（   ）

设$x,y\in$R，向量$\overrightarrow{a}=(x,1)\overrightarrow{,b}=(1,y),\overrightarrow{c}=(2,-4)$且$\overrightarrow{a}\perp \overrightarrow{c},\overrightarrow{b}//\overrightarrow{c}$，则$|\overrightarrow{a}+\overrightarrow{b}|$（    ）

   I  have a good friend．1 name is Peter．We study in Beijing Sunshine Secondary Schoo1．We are in the same(同一个)class．He sits in front of 2 ．His favourite lesson is Music．He  3many CDs．He likes 4 music very much．He likes playing football , t00．After school we  often   play  football in the  5 ．He is very helpful．We often help each 6 ．
   Peter  is  not a Chinese．He is from 7  ．He comes to Beijing 8  his family．His father is  a doctor and his mother is a nurse. They work from Monday    9   Friday．At weekends，his mother  likes shopping and his father likes fishing．Sometimes they go to the park．They all like Chinese  food．They  10   very happy．

西班牙在美洲的主要黄金来源地是新格拉纳达。到1600年，从这里出口了400多万盎司的黄金。新格拉纳达的黄金产量逐步上升，到18世纪，其产量约为16世纪产量的三倍。这些黄金的流入直接导致西班牙（    ）