命题甲：动点P到两定点A、B的距离之和|PA|+|PB|=2a(a＞0，常数)；命题乙:P点轨迹是以两定点A、B为焦点的椭圆.则命题甲是命题乙的( ) A.充分不必要条
The earthquake and the suffering has caused will affect us greatly for a long time. A.that B.it C.which D.what
Technology today has stolen away our voices and robbed our children of memories. I’ve been keeping count of how often people sing around the house these days. The fact is, they don’t. My ea
已知函数，，则是 A．奇函数且在上单调递增 B．奇函数且在上单调递减 C．偶函数且在上单调递增 D．偶函数且在上单调递减
. ________ on the radio or see on TV is only a small part of all the wonderful music that is waiting for us. A. What B. That C. Which D. All what
生物催化剂与无机催化剂都具有的特点是 ( ) A．高效性 B．专一性 C．需要适宜温度和pH D．能催化化
Many things impossible in the past are very common today. A. consider B. considering C. considered
2010年五一期间，很多中国人选择了走出家门外出旅游。消费者掀起节日旅游的最主要原因是 （ ） A．人们消费观念的改变
