根据文意，补全所缺单词，词首字母已给出。
Overhead bridges can be seen in many parts of Singapore，in the places where traffic is very h _____ and crossing the road is not safe.
These bridges can help people cross roads s _____ .Overhead bridges are used in very much the same way as zebra crossings(斑马线).
They are more efficient(效率高的)，t _____ less convenient(方便的)because people have to climb up a lot of steps.This is inconvenient to the old.When people u _____ an overhead bridge，they do not hold up(阻挡) traffic.But when they cross a busy road using a zebra crossing，traffic is held up.This is w _____ the government(政府)has built many overhead bridges to help people and k _____ traffic moving at the same time.
The government of Singapore has s _____ a lot of money building these bridges.For their own safety，people should be advised to use them instead of rushing across the road.Old people may find it a little d _____ climbing up and down the steps，but it is still much safer than walking across the road w _____ all the moving traffic.
Overhead bridges are very useful.People， both old and young，should always use them. This will stop accidents from h _____ .
Key:
1.heavy
2.safely(作状语应用副词形式)
3.though(此处表让步关系，意为“虽然”)
4.use
5.why(此处表达“这就是……的原因)
6.keep
7.spent(spend time /money in /on doing sth.意为“花时间/金钱做某事”，其中in常省略)
8.difficult
9.with
10.happening(stop...from doing)意为“阻止/防止……去做某事”)
