Nature provides 31 with the means of survival.
答案：(B) them
them 代替前面提到的複數概念 all forms of life，作 provides 的間接受詞；it（單數，不匹配複數）、this（指示代名詞不用於此）、which（疑問/關係代名詞不適用於此）都不合。
本題大考中心未公布逐題答對率，以下不談數據，只談觀念。
四個選項都是很短的代名詞或關係詞，如果沒回頭確認它指的是誰、是單數還是複數，就只能猜。
先看句型：Nature provides ___ with the means of survival.provide somebody with something（提供某人某物）是固定的搭配，所以空格要填的是「被提供的對象」，而且要是受格。再回頭找那個對象：前一句是 All forms of life have an instinctive urge to survive.（所有的生命形式都有求生的本能。）——所以大自然提供生存手段的對象，就是那些生命形式，是複數，填 them。
it：單數，與 all forms of life 這個複數對不上。this：指示代名詞，通常用來指前面提過的一整件事，而這裡要的是「一群對象」，而且 provide this with 不成說法。which：關係代名詞或疑問詞，本句是完整的直述句，沒有位置給它。
provide sb with sth（提供某人某物）、provide sth for sb（為某人提供某物）、an instinctive urge（本能的衝動）、the means of survival（生存的手段）、all forms of life（所有的生命形式）、survive（生存）。
All forms of life have an instinctive urge to survive. Nature provides 31 with the means of survival. We have learned much about survival from 32 forms of animal life.
Lizards, 33 can change the color of their skin and 34 the trees and leaves around them. 35 , they cannot be detected by other animals that threaten them. Nature provides other forms of protection 36 environmental dangers.
Human beings, too, 37 special devices to protect 38 . Their skin is very 39 to temperature changes. 40 warm weather, sweating helps humans regulate their body temperature.