单项选择题
Overhead bridges are found in many parts of Singapore, especially in places where traffic is heavy and crossing the road is dangerous.
The purpose of these bridges is to enable people to cross roads safely. Overhead bridges are used in very much the same way as zebra crossing(斑马线). They are more efficient although less convenient because people have to climb up a long flight of steps. This is inconvenient especially to older people. When people use an overhead bridge, they don't hold up traffic. However, when they cross a busy road using a zebra crossing, traffic is held up. This is why the government has built up many overhead bridges to help people and to keep traffic moving at the same time.
For their own safety, people should be encouraged to use them instead of risking their lives by dashing(闯) across the road. Old people, however, may find it a little difficult climbing up and down the steps, but it is still advisable for them to use overhead bridges.
Overhead bridges serve a very useful purpose. This will prevent unnecessary accidents and loss of life.
The advantage of overhead bridges is that ______.
A．they
F.people
G.they
H.they
