A：在這句中，as 是當準關係代名詞，其作用相當於 which，是用來代替句中整個主要子句 (而不是某個先行詞)。例如：
- She is a bad girl, which was mentioned before. (她是個壞女孩，這一點以前已提過)
= She is a bad girl, as was mentioned before.
在上句中，which 與 as 可以劃上等號，它們都是代替整個主要子句 “She is a bad girl”，而不是只有 “girl”。
然而，as 當準關係代名詞時，有一特殊用法是 which 所沒有的，那就是：As 所引導的形容詞子句，可與主要子句互換位置，但 which 所引導的形容詞子句，卻不可與主要子句互換位置。以問題中的句子為例：
- As is usual around the world, men love beautiful women. (男人愛美女，這一點舉世皆然) (正)
- Which is usual around the world, men love beautiful women. (誤)
所以，這句的原句應為：
- Men love beautiful women, as is usual around the world.
= Men love beautiful women, which is usual around the world.