下图为某物体的x-t图象，在第1s内物体的速度是___，从第2s至第3s内物体的

     Mr. and Mrs. William are having their holiday in Rome. It is an old city, and a new city, too. They are
staying in a very good hotel in the center    1    the city.
     Rome is    2    a beautiful city. The air    3    fresh; the sky is blue and clear. Cool wind makes people 
    4    relaxed. Every day in the morning, the Williams through the hotel windows,    5    the cars coming and
going on the streets. They also like to walk around in the city. They walk from one place to    6   . Sometimes
they go into a    7    and buy some presents    8    their friends.
      People in Rome are kind and friendly. The Williams like to talk with the people and each year they    9    
some new friends in the city. Mrs. William says: "Rome is the best place    10   ."