考点：as 与 which 引导定语从句辨析
一、位置与固定表达区别
| 对比维度 | as | which |
|---|---|---|
| 在句中的位置 | 句首、句中、句末皆可 | 通常只能置于主句之后 |
| 语义倾向 | 正如，如同（符合预期） | 这一点（常指导致的结果） |
| 常见固定结构 | as is reported, as we expected, as is well known | 无固定搭配，常连接顺承或因果事实 |
二、常见易错题型
- 句首空格：
____ is often the case, he was late again.$ o$ 必须填As，不可填 Which。 - 逗号后表达意料之外的结果：
He failed in the exam, ____ surprised everyone.$ o$ 填which。