小凌同学代表小组发言时说：“这是个独特的民族，它是战争狂徒，用战车把宗教传播到西亚、北非等地，穆斯林的足迹从此遍及四方；它又是文明使者，用嘴巴将东西方文化传承、传播，某种数字因此冠上它的大名。”这个“独特民族”指的是（    ）       

下列关于燃烧现象的描述中正确的是（  ）

方程$x^2+y^2+ax-2ay+2a^2+3a=0$表示的图形是半径为r（$r>0$）的圆，则该圆圆心在(        )

Dear Lucy,
   We are back in Garden City now. We had    1   good trip.
   I    2  to collect my photos yesterday. They    3great! I showed these photos    4  my classmates. They all   5  them.
   There is a photo of Ben and Simon  6   the Great Wall. There is one of you and  7in the Forbidden City(紫禁城).
We really enjoyed    8vacation. We were sad(悲伤)to   9   you.
   You must   10and visit us in Garden City at Chinese New Year.
                                                                                                                                                          Love,
                                                                                                                                                          Kitty