People began making clocks over 500 years ago. The first clocks had only one hand---the hour hand. At a later time the clocks had the minute hand. The first clocks were big and heavy. Some rich people had servants   to carry the clocks when they were out. Time passed and clocks became smaller. Bells became a part of some large clocks in cities and towns. They were for people unable to see the clock. Some clocks were in large towers . Some of them are 400 or 500 years old now. Big Ben in London is a very famous tower clock. Now many people have alarm clocks   to wake them up to go to work or go to school. So clocks are the very important part of people's life. Alarm clocks can help people   _   .
work hard wake up see the time go to bed