“天宫一号”和地面之间的信息传播是通过 ____波来实现的，这种波在真空中的传播速度是　 ____m/s．而潜水器是利用水声通讯系统发射声波与海面上的母船通信的，那么处于深海中的潜水器与太空中的“天宫一号”之间 ____（选填“能”或“不能”）只利用该水声通讯系统直接对话．

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    In 1978, I was 18 and was working as a nurse in a small town about 270 km away from Sydney, Australia. I was looking forward to having five fays off from duty. Unfortunately, the only one train a day back to my home in Sydney had already left. So I thought I'd hitch a ride (搭便车).

    I waited by the side of the highway for three hours but no one stopped for me. Finally, a man walked over and introduced himself as Gordon. He said that although he couldn't give me a lift, I should come back to his house for lunch. He noticed me standing for hours in the November heat and thought I must be hungry. I was doubtful as a young girl but he assured （使…放心）me I was safe, and he also offered to help me find a lift home afterwards. When we arrived at his house, he made us sandwiches. After lunch, he helped me find a lift home.

    Twenty-five years later, in 2003, while I was driving to a nearby town one day, I saw an elderly man standing in the glaring heat, trying to hitch a ride. I thought it was another chance to repay someone for the kindness I'd been given decades earlier. I pulled over and picked him up. I made him comfortable on the back seat and offered him some water.

    After a few moments of small talk, the man said to me, “You haven't changed a bit, even your red hair is still the same.” I couldn't remember where I'd met him. He then told me he was the man who had given me lunch and helped me find a lift all those years ago. It was Gordon.