efore单独使用有两者情况:1.放在句尾.句子是否定句.这时该句常常用现在完成时.如: I have never seen him before. 2.before 后不跟句子,那before 就是个介词,而不是连词了.其后就要用动名词.句子时态看具体情况而定. He said nothing before leaving.
before单独使用有两者情况:1.放在句尾。句子是否定句。这时该句常常用现在完成时。如: I have never seen him before. 2.before 后不跟句子,那before 就是个介词,而不是连词了。其后就要用动名词。句子时态看具体情况而定。 He said nothing before leaving....