用括号内动词或词组的适当形式填空
More than 5, 000 used bikes ______ (collect)since the two brothers set up the organization.
Since the cause of this disease ______ (discover), now we need to develop the medicine to treat it.
Over the past ten years, this town ______ (hit)twice by earthquakes.
-Will the lecture be held at 4 0'clock this afternoon?
-No. It ______ (putoff) till tomorrow afternoon.
Her novel is very popular among people of all ages; so far it ______ (translate)into 25 languages.