题目内容：

    Cities such as New York, Washington, Boston and San Francisco have launched bike-share programs to ease traffic jam, improve public health, and cut carbon emissions (排放). Cyclists in those cities tend to choose bike-sharing to make their trips to office or home faster, cheaper, and more fun. Last year, U.S. bike-share riders completed nearly 46 million trips—more than twice as many trips from the previous year.

Yet despite these programs’ advantages and popularity, there are still huge challenges. Take, for instance, the distribution (分布) of bikes. The living area face shortages of bicycles in the morning rush, while business districts do not have enough bikes in the evening. What’s more, parking places can be full at certain hours, making it difficult for riders to return the bikes once they’ve reached their destinations.

Solving this problem is not easy. David B. Shmoys and his colleagues set out to develop complex algorithms(算法) and advanced analytics(逻辑法) to solve the challenges of bike-share operations.

One area in which the methods were applied was the Bike Angels program. As part of the program, cyclists can be rewarded with points by renting or returning bikes at certain high-need stations. Today, Bike Angels accounts for roughly 30 percent of bike rebalancing in New York City. It has greatly improved customer satisfaction which, in turn, has more riders. And more importantly, this form of rebalancing comes with a much less carbon emissions, because less box trucks are needed to move the bikes!

David B. Shmoys and his colleagues applied algorithms and analytics to solve other problems, too. However, they can not solve every new transportation problem. They have many limitations, including incomplete information. That is, David B. Shmoys and his colleagues only observe the realized rentals (returns) at stations at which bikes were available, not those that were blocked due to the imbalance of the system.

1.Which is not one of the advantages of bike-share program?

A.It helps people save money.

B.It helps improve the air quality.

C.It provides more bikes for cyclists.

D.It helps people build up their bodies.

2.What is mainly talked about in paragraph 2?

A.Riders do not want to return the bikes.

B.The distribution of bikes is a big problem.

C.People do not have enough bikes in the morning.

D.The bike-share program is very popular in New York.

3.What do we know about the Bike Angels program?

A.It had more users due to the algorithms.

B.It increased the use of box trucks.

C.It awarded riders cash for renting bikes.

D.It re-balanced all the bikes in New York.

4.What does the underlined word “they” in the last paragraph probably refer to?

A.other problems

B.carbon emissions

C.algorithms and analytics

D.Transportation problems