It was the last lesson before the holidays. The students were very happy. Their English teacher was very happy, too. The teacher played interesting games with them. They also sang some nice s{#blank#}1{#/blank#}. Everyone had a smile on the face. The teacher went to the blackboard and wrote "SMILES" on it. "This is one of the l{#blank#}2{#/blank#}words in English", he said to the class. The whole class laughed, and then one girl s{#blank#}3{#/blank#}up and said, "Why is it one of the longest words in English?" The teacher said n{#blank#}4{#/blank#}for a while. Then he smiled and said, "B{#blank#}5{#/blank#} there is a mile between the first letter and the last."

    The earth is a {#blank#}1{#/blank#} (行星)and it goes around the sun. Seven others also go around the sun. {#blank#}2{#/blank#} (没有一个)of them has an {#blank#}3{#/blank#} (环境)like that of the {#blank#}4{#/blank#} (地球), so scientists do not think they will find life on them. The sun and its planet are called the {#blank#}5{#/blank#} (太阳的)system, and ours is a small part of a much larger  {#blank#}6{#/blank#} (群, 组)of stars and planets, called the {#blank#}7{#/blank#} (星系).

    Scientists have also {#blank#}8{#/blank#} (发现)many others in the {#blank#}9{#/blank#} (宇宙). They are very far away and their {#blank#}10{#/blank#} (光)has to travel for many years to reach us. So how large is it? It is impossible to imagine.