I have two good friends．They are Gina and Jenny, and they are twin(双胞胎之一的)sisters．They come from Singapore．They are 12 years old．They can speak English and Chinese．

    Now the twins are in China．Their family are in China，too．They live in Shanghai．There are five people in their family．They are their parents，their brother and them．Their mother is a doctor．Their father is a teacher．Their brother Alan is very young．He is four years old．He can't go to school．

    Gina，Jenny and I are in the same class．Every day, we walk to school and talk a lot．They say China is a very good place and they like China．

根据材料内容选择最佳答案。

拥有近1.8亿亩耕地的黑龙江省，素有“中国粮仓”的美誉，黑龙江的地表结构特征可概括为（ ）

“苦干诚可贵，巧干价更高；制造到创造，价值千倍遥。”中国要赶超发达国家，必须实现由“中国制造”到“中国创造”的转变。 

一个物体在光滑水平面上以初速度v₀做曲线运动，已知在此过程中只受一个恒力F作用，运动轨迹如图，则由M到N的过程中，速度大小的变化为（   ）