2011年7月23日，甬温线D301次列车与D3115次列车发生追尾事故，事故共造成了40人死亡，200多人受伤，从而引发了广大民众对我国高铁运行安全的关注和担忧．若在水平直轨道上有一列以额定功率行驶的列车，所受阻力与质量成正比，由于发生紧急情况，使最后几节车厢与车体分离，分离后车头保持额定功率运行，则（   ）

下面四幅图是两个物体不同时刻在太阳光下的影子，按照时间的先后排序正确的是（）

根据短文内容，判断下列句子是否正确，对的涂（A），错的涂（B）。
    Kate is a little girl. She's only five. She is not at school. She doesn't know how to read or write. But her sister Mary is a student. She knows how to read and write.
    One day, Mary sees her little sister in the room. She is at the table. There is a pencil in her hand. She is writing. “What are you writing, Kate?” she asks. “I'm writing to my friend, Rose.” says Kate. “But how can you? You don't know how to write.” says her sister. “Well.” says Kate, “It doesn't matter. Rose doesn't know how to read, either(也).”
____ Kate doesn't go to school because she is too young.
____ Kate and Mary arefriends.
____ One day, Kate is writing to Mary.
____ Kate can't write.
____ Rose can read.

下图为某地区的地质剖面图和水循环示意图。读图，完成下列问题。