题目内容：

For more than fifty years, a worker was forced to sit on the back of a truck and slowly drop plastic barriers（障碍）

to set out lanes（车道）on the Golden Gate Bridge in San Francisco. Every day, their direction changes to control the traffic, meaning an employee had to go through the difficult task every twenty-four hours.

But a new piece of machinery means the work can be completed in a matter of minutes. A new “zipper truck” has been introduced. The vehicle lays and moves a lane barrier as it drives over the bridge. Last weekend, the bridge was closed so the new safety barrier, designed to reduce the dangers of head-on crashes, could be set up.

For the longest period in its nearly eighty-year history, the bridge was closed early Saturday to all but walkers, cyclists and buses to set up the barriers on the 1.7-mile bridge. A survivor of a 2008 head-on crash on the bridge spoke Sunday from a wheelchair to help introduce the new barrier, made of steel-clad concrete（铜包混凝土）blocks that can move across the bridge’s six lanes to meet traffic needs.

Gr. Grace Dammann pushed for a safer barrier since becoming unable to walk after the accident. She said she decided to drive near the middle of the bridge, which was called the “suicide（自杀）lane”, because she and her daughter were running late. Brian Clark, who was driving in the opposite direction, had just learned his father had cancer. “He suddenly lost control of the wheel, crossed over and hit my car,” Dammann said.

She said she and Clark became friends as they persuaded（说服）the government to use the MYM30 million barrier. “I am so thankful,” said Dammann, who came to the ceremony with Clark.

“Clark and I thank you.”

1.What is the zipper truck for?

A. Building bridges.    B. Repairing the road.

C. Carrying plastic barriers.    D. Setting up safe lane barriers.

2.What can we infer about the Golden Gate Bridge?

A. It is being repaired now.    B. It is a bridge with eight lanes.

C. It had very dangerous lanes before.    D. It is too old to be used at the moment.

3.What do we learn about Dammann and Clark?

A. They organized the ceremony.    B. They are both government officials.

C. They designed the new zipper truck.    D. They were in favor of the new barrier.

4.What is the text mainly about?

A. A worker on the Golden Gate Bridge.    B. A great bridge in San Francisco.

C. A new safer barrier system.    D. A serious traffic accident.