题目

七选五Today's families are busy. Mom and Dad are both working, the kids are involved in a variety of activities, and there is little time to enjoy being a family. What can you do to build some family unity(和睦)? How can you prevent those you love from not knowing each other? It takes time and patience, but it is definitely possible! If it's not possible to have them every night, make sure that you eat together as a family at the dinner table at least twice a week. If you need to cut something out of your schedule to achieve this, then do it.Make a rule that all members of the family are一般地说，干旱条件下育成的作物品种，适于在干旱地区种植；潮湿条件下育成的作物品种，适于在潮湿地区种植。在这里，干旱和潮湿条件所起的作用是   （    ） A．诱发基因突变       B．引起染色体变异     C．选择基因型         D．导致基因重组