is加過去分詞是什么時(shí)態(tài)

　　Eight hours on a bus is no joke, is it.

　　坐８?jìng)�(gè)小時(shí)的公交車可不是鬧著玩兒的，對(duì)吧。

　　He is in no doubt as to what is needed.

　　他對(duì)需要些什么心中有數(shù)。

　　It is a country where corruption is rife.

　　這是個(gè)腐敗成風(fēng)的國(guó)家。