题目内容：

With the approval of the Singapore government, a company called nuTonomy has become the first-ever to test self-driving cars with the public. Interested people could sign up for a free trial run at no cost. When they received an invitation from the company, they could book a ride on the driverless taxi service from their smartphones.Not surprisingly,the rides proved very popular,with dozens of customers eagerly trying out the cars each day.

Driverless cars are a great option for those who do not know how to drive and for those who do not enjoy driving.Some researchers even believe that such cars can make road travel safer by reducing human errors.But since driving requires many of our senses to be on alert（高度警觉）, replacing that by machines is easier said than done.

The environment in which cars operate is constantly changing—from roads and pedestrians to co-travelers. A driverless car needs special equipment to analyze its surroundings. Then, it must translate that information into a practical route and safe travel. To be truly autonomous, a car has to do this independently without human input. Today, some cars have a certain degree of autonomous functions. But even the completely automated vehicles still require a driver to take back control under uncertain conditions.

The island city-state is well known for excellent roads and drivers who obey the rules. This has made it ideal for real-world testing and feedback. The government has encouraged research in autonomous vehicles, since it can improve safety and potentially reduce the traffic burden as well.

1.What is the text mainly about?

A. Driverless cars travel safely on the road now.

B. Driverless taxis have been tasted in Singapore.

C. Singapore is the best place to produce driverless cars.

D. Singapore government has decided to use driverless taxis.

2.Which factor matters most when a driverless car travels on the road?

A. The input from human.

B. The directions of its users.

C. The changing environment.

D. The mood of the co-travelers.

3.What can we infer about the driverless curs from Paragraph 2?

A. They have many human senses.

B. They are not absolutely safe on road.

C. They can make people enjoy driving.

D. They are popular with skilled drivers.

4.Why is Singapore a suitable place to test the car?

A. Because it has a small population.

B. Because the pedestrians obey the rules.

C. Because it is famous for its car industry.

D. Because it owns nice roads and polite drivers.