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)?

    Crocodiles (鳄鱼) lay their eggs and leave them under leaves or sand. Baby crocodiles use their teeth {#blank#}1{#/blank#} (break) their way out of the shells.

    Crocodiles are {#blank#}2{#/blank#} (find) in Australia {#blank#}3{#/blank#}  America. They spend most of their time {#blank#}4{#/blank#} (lie) around in the rivers. The crocodile's long tail is used when the animal is swimming. It is {#blank#}5{#/blank#}  excellent weapon(武器). It can be used to strike(打击) the enemies. One blow will knock down a man or even a big animal at once. The crocodile has a hard neck. It cannot turn {#blank#}6{#/blank#}(it) head from side to side, so it can only see something in front of itself. The crocodile has its teeth {#blank#}7{#/blank#}(clean) by the crocodile bird. For its food this bird takes the bits in the crocodile's mouth. This helps the crocodile a lot, {#blank#}8{#/blank#} it cannot move its tongue up and down. With its terrible {#blank#}9{#/blank#} (tooth) it catches its food. The food may be a fish, an animal, or even a {#blank#}10{#/blank#} (careful) man.