How much: $ 6 for a 24-hour pass.

　　How it works: The first 30 minutes are included in the pass; $ 2 for the second 30 minutes; $ 4 for the third 30 minutes; later $ 8 for every half an hour.

　　We are volunteers. If you want to know more information, please contact us.

21. According to the text, the City Bike program _______.

　　A. was first set up in New York

　　B. has a long history in America

　　C. develops very fast all over the world

　　D. is very popular in American cities

22. Which of the following bike-share programs costs the riders most?

　　A. Nice Ride Minnesota B. Citi Bike

　　C. Hubway D. Divvy Bikes

23. If you visit Boston by riding Hubway bike for 3 hours, you have to pay ____.

　　A. $6 B. $ 20 C. $ 36 D. $ 30

　　　　　　　　　　　　　　　　　　　　B

　　Dubai（迪拜）is one of the economically richest places in the world. With its numerous malls, hotels, and beautiful beaches, Dubai has always been a popular holiday destination. This city was visited by around 5 million tourists each year. The government wanted to increase this number to 15 million. However, Dubai has only 45 miles of coastline, which is nowhere enough for so many people. To solve this problem, an island that looked like a palm tree was built in 2006, and named the Palm Jumeirah.

　　The plan for the island was extraordinary. It was to host several hotels, shopping malls, restaurants, and homes. Although the initial plan was to build the island from concrete（水泥）, a decision was taken to create it from sand and gravel（砾石）, so as to give it a natural look.

To make sure that this project was a success, the best engineers from across the world were employed. Engineers from Holland formed the majority in this group. To begin with, the engineers calculated the strength of storms at sea, and also the expected amount of rise in water levels due to global warming. And then they found that, the proposed location for the island was neither very wide nor deep.