2 . The slow growing lichen (地衣) and mushrooms upon which the reindeer depend for survival are not found in plantations. So, the death of one __________ mean the death of the other, and an uncertain future for an entire people. (用适当的词填空)

3 . Some scientific evidence suggests musical training before the age of seven ________ have a significant impact on the brain’s development. (用适当的词填空)

4 . It ________ be really cold in November in Hefei though we usually have warm and sunny days. （用适当的词填空）