B.as well as
John plays foot ball as well as,if not better than,David.
如果John的football 玩得沒David好,那就是跟他一樣好.
如果沒有后面那一句
John plays football （A) as well.意思就是 John 也玩 football.
John plays football (C) so well.意思是 John 的 football 玩得很好.
John plays football (D) so well as.so well as 不是一個明確的短語.
只有(B) as well as 是正確.
因為在這里,John 被用來和David作比較.
"as well as" 意思就是 跟____一樣好
歡迎追問.追問as well as 不是放句中的嗎 為什么后面還加逗號啊
回答如果沒有那句"if not better than" 那么
John plays football as well as David 就是正確的.
可是這里有 if not better than,多了這么一個形容句,所以它之前 (as well as 之后) 要有個逗號分割開來.
順帶一提,其實通常在兩個逗號之間的形容句都是比較不重要的,不過加了的話會使整個句子看起來更有深度,寫作多用用會不錯.