Great inventions change the world. They help people live a better life. The following {#blank#}1{#/blank#}(be) three of the most important inventions in history.

    The wheel may be the greatest invention in history. Travelling became faster and {#blank#}2{#/blank#}(comfortable) after its invention. Several thousand years ago, people started to use wheels on carriages. In {#blank#}3{#/blank#} early 19^th century, the first trains began to carry passengers.{#blank#}4{#/blank#} the wheel, we would not have these inventions.

One of the first {#blank#}5{#/blank#}(practice) telephones was invented by Alexander Graham Bell in1876. Since then, people have been able to speak to each other over long distances. Today {#blank#}6{#/blank#}(million) of people across the world own mobile phones. They allow people {#blank#}7{#/blank#}(keep) in touch with each other anytime , anywhere.

    Thomas Edison developed the first useful light bulb in 1879. With light bulbs, people can do as many things in the evenings {#blank#}8{#/blank#} they can in the daytime. Can you imagine {#blank#}9{#/blank#}(live) a life without {#blank#}10{#/blank#}(they)?

—No. Peter sings as______ as him.

—It's             . Both the air and the water are badly polluted.