--Do you know when the Chinese custom_________ from? --It's hard to say. But its characteristics__________ the Tang Period.

Some modem paintings are _____ my understanding;  I simply can't understand what the   painters really want to tell us.

 —I have telephoned him twice but I couldn’t get through.—I think that the line _____ be being worked on today.

 The supermarket sells many foods that have been_____ , so it is convenient to feed your stomach.

It is said that many streets in this city have been ______ for cultural protection.