动词不定式的进行时，表示“正在迎接，正在欢迎”的意思。

 He seems to be worrying about something. 他似乎正在担心什么事。

Don't pretend to be working hard. Just do what you should. 不要假装努力工作。做你该做的事。

She was supposed to be reading at home, but her mother found her in the park.

她本来应该在家里读书的，可是她妈妈发现她在公园里。