简述低焦油育种策略。
参考答案：
1）直接针对焦油量进行育种
2）通过降低烟碱来降低焦油
3）提高烟碱以降低焦油/烟碱的比值
-----What do you think of the materials _____ these clothes were made? ----- They feel _____.
A．for whom; well
B．into; soft
C．of which; soft
D．in which; good
防鼠板材料可选用（）
A、木版
B、塑料板
C、硬纸板
D、以上都不是
