②给出“ 介词 +___+句子”,介词后不能用that,考察介词+which/whom引导的定语从句。 ●Many lessons are now available online, from ___ students can choose for free. 【“介词+关系代词”引导的非限制性定语从句,先行词是many lessons(指物),关系代词用which】 ③...