录音中女生先说：So because of the permafrost, none of the plants that grow there can have deep roots, can they? 教授回答说：No, and that's one of the reasons that shrubs survive in the Arctic. 根据对话可知，因为北极有永久冻土层，所以生长在北极的植物都没有深层根系，这是灌木能在北极生存的一个原因。由此可知灌木是没有深层根系的，D 选项正确。后文教授又提到：So there's been increased nutrient production in the winter. And that's what's responsible for the growth of shrubs in the summer and their spread to new areas of the tundra. 即冬季土壤中发生的生物过程使得土壤中的营养元素增加，促使灌木在夏季加速增长，并蔓延到新地区。这说明灌木能吸收的营养元素增加，对应 C 选项。综上，本题选 C 和 D。

答案: CD