表示正在發(fā)生的事情或進(jìn)行的動(dòng)作，常與now,listen,look等詞連用，結(jié)構(gòu)是主語+be動(dòng)詞(am, is, are)+動(dòng)詞ing.

　　如：It is raining now.

　　外面正在下雨

　　It is six o’clock now.

　　現(xiàn)在6點(diǎn)了

　　My parents are reading newspapers in the sitting room.

　　我父母正在客廳看報(bào)紙

　　Look! The children are having a running race now.

　　看！孩子們正在賽跑

　　問句將be動(dòng)詞移前，否定句在be動(dòng)詞后+not.