Only time will tell if the treatment has been successful.

　　只有時間才能證明這種療法是否成功。

　　The system has been in operation for six months.

　　這個系統(tǒng)已經運行六個月了。

　　The company has been investing in new plant and equipment.

　　這家公司一直在投資購置新機器和設備。

　　A new system has been devised to control traffic in the city.

　　控制城市交通的新系統(tǒng)已經設計出來。

　　Digital television has been around for some time now.

　　數(shù)字電視已經面市一段時間了。