当今世界的主题是（　　）

(____) It's a programme about China.

(____) We've got lots of food.

(____) Thank you for talking to us.

(____) She couldn't read or write.

(____) He didn't have any legs then.

Hello, I’m Linda. I have four friends. They are Ann, Lisa, Tom and Peter. Ann lives near school. She comes to school on foot. There is an underground station near Lisa’s home. She comes to school by underground. Tom lives far from school. He comes to school by bus. Peter likes riding. He comes to school by bike.

⒈ ____ ____

⒉____ ____

⒊____ ____

⒋____ ____

设$x,y,z$是不相等的三个数，则使$x,y,z$成等差数列, 且$x,z,y$成等比数列的条件是（   ）