has been是什么時態(tài)

　　A peaceable settlement has been reached.

　　已經(jīng)實現(xiàn)和解。

　　The gene for asthma has been identified.

　　哮喘病的基因已被識別。

　　Since 1977 otter hunting has been illegal.

　　捕獵水獺1977年以后就被列為非法了。