①若m⊥α，n⊥α，则m∥n；        

②若α∩γ=m，β∩γ=n，m∥n则α∥β；

③若α∥β，β∥γ，m⊥α，则m⊥γ

④若γ⊥α，γ⊥β，则α∥β．

其中正确命题的序号是（  ）

世界上淡水资源最丰富的大洲是（　　）

     On a cold afternoon in winter, Robert was walking on the bridge. There was hardly any   1   on the river. Near the bridge, however, there was a small canoe(独木舟), with a boy in it. He was not    2   many clothes. He was going to walk when he heard a cry, “Help!” He looked down and saw the boy was in water and his canoe was far away.
    Robert was a good   3. Taking off his clothes, he jumped into the river. The cold water made him tremble(颤抖)all over. Soon he 4  the boy and started to swim towards the river bank. Just then he saw a motor boat under the bridge. There were some people on it, all 5 in his direction. Robert 6  to swim towards the boat.
    “Help me,” he shouted  7 he got near the boat. He looked up into a row of faces. “Why?” he thought. “They look so   8 .” Silently they helped the boy into the boat. But they did not move to save Robert.
    “Aren't you going to help me  9  , too?” Robert asked.
    “You!”said one of the men, who was standing next to a large camera, “Why, we were making a film and you spoiled (搅乱) the whole afternoon's work! You can   10  in the water.”