has been 過去分詞是什麼時態

The system has been in operation for six months.

這個系統已經執行六個月了。

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'新系統已經設計出來。

Digital television has been around for some time now.

數字電視已經面市一段時間了。

A new advance has been made in the control of malaria.

在控制瘧疾方面已取得新的進展。