参考答案：covered with a heavy wax coating

解析：[定位] 由题干中的evergreens，survive the winter和fluid inside their cells定位到第五个小标题下第2段第1、2、3句内容The evergreens．．．survive winter because…leaf is covered with a heavy wax coating and the fluid inside their cells contains substances that resist freezing．．．[精解] 此处需要填入原因状语从句的谓语成分。本段第2句说明了常青植物的叶子是如何能够抵御寒冷的；题干中的cold—resisting substances与原文中的substances that resist freezing属同义转述。故答案为covered with a heavy Wax coating。