题目

________ the heavy rain and flooding, lots of people have been forced to leave their homes. A. In spite of                          B. Due to C. Because                              D. Since 答案：B下列可遗传变异一定不引起染色体上DNA碱基对排列顺序发生改变的是 A．基因突变 B．基因重组 C．染色体结构变异 D．染色体数目变异