1．(2020·浙江7月高考)Over thousands of years, they began to depend less on could be hunted or gathered from the wild, and more on animals they had raised and crops they had sown.
解析：what 分析句子结构可知，介词on后是宾语从句，从句中缺少主语，且表示“……的事物”，应用what引导。
2．(2019·全国卷Ⅰ)While they are rare north of 88°， there is evidence they range all the way across the Arctic, and as far south as James Bay in Canada.
解析：that 分析句子结构可知，设空处引导同位语从句，解释说明evidence的内容，从句中不缺少成分且意义完整，故填that。
3．(2018·浙江11月高考)It is possible caffeine may cause birth defects (缺陷) in humans, too.
解析：that 分析句子结构可知，该句是一个主从复合句，it作形式主语，真正的主语是设空处引导的从句，故填that。
