质量为0.5kg的物体，运动速度为3m/s，它在一个变力作用下速度变为7m/s，方向和原来方向相反，则这段时间内动量的变化量为（   ）

下图为DNA分子结构的模式图，据图作答：

    A boy lost his arms in an accident and his father lost his life. Since then, he had to1the arms of his younger brother. Except for writing with his toes(脚趾头), he could hardly do  2in his life.
    As the two brothers grew up together, they had lots of 3 and they often argued(争吵). Then one day, his younger brother 4 him. So he was very sad and didn't know 5 to do.
    A girl lost her hands because of a fire. Though her elder sister wanted to 6 her, she decided to be completely independent (独立的). At school, she always studied hard. Once she wrote the following in her composition, “I am 7. Though I lost my hands, I still have legs. Though my wings are broken, my heart can still fly.”
    One day, the boy and the girl were both invited 8 a television interview program. They both were asked to write something on a piece of paper with their toes. The boy wrote “My younger brother's arms are my arms”9 the girl wrote "Broken wings, 10 heart”.

读“中国东部雨带示意”图，如在7月以后，雨带仍未推移进入Ⅰ地区，我国东部地区将可能产生灾害的状况是（   ）