Why can't I roslaunch?

edit

Hi, everyone. Im learning ROS tutorials on wiki.When I first use roslaunch according to the beginner level tutorial, there is something wrong. I don't know why it shows that there is a syntax error at line 1,column 3 cause I just copy the code on tutorial. Please tell me why.

input:

roslaunch beginner_tutorials turtlemimic.launch

output:

logging to /home/bit/.ros/log/........long number....../roslaunch-bit-auto-6902.log
checking log directory for disk usage. This may take awhile.
press ctrl-c to interrupt
done checking log file disk usage. usage is <1GB

/the following r red words/

invalid roslaunch xml syntax: syntax error: line 1,column 3
the traceback for the exception was written to the log file

This is the turtlemimic.launch file.

   1 <launch>
   2 
   3   <group ns="turtlesim1">
   4     <node pkg="turtlesim" name="sim" type="turtlesim_node"/>
   5   </group>
   6 
   7   <group ns="turtlesim2">
   8     <node pkg="turtlesim" name="sim" type="turtlesim_node"/>
   9   </group>
  10 
  11   <node pkg="turtlesim" name="mimic" type="mimic">
  12     <remap from="input" to="turtlesim1/turtle1"/>
  13     <remap from="output" to="turtlesim2/turtle1"/>
  14   </node>
  15 
  16 </launch>