solution: Evelyn covered more distance in less time than Briana, Debra and Angela, so her average speed is greater than any of their average speeds. Evelyn went almost as far as Carla in less than half the time that it took Carla, so Evelyn's average speed is also greater than Carla's. Therefore, $\boxed{\text{Evelyn}}$ is our answer.
prompt.content: <|im_start|>system
  You are a helpful assistant.<|im_end|>
  <|im_start|>user
  The results of a cross-country team's training run are graphed below. Which student has the greatest average speed? [asy]
  for ( int i = 1; i <= 7; ++i )
  {
  
  draw((i,0)--(i,6));
  }
  
  for ( int i = 1; i <= 5; ++i )
  {
  
  draw((0,i)--(8,i));
  }
  draw((-0.5,0)--(8,0), linewidth(1));
  draw((0,-0.5)--(0,6), linewidth(1));
  label("$O$", (0,0), SW);
  label(scale(.85)*rotate(90)*"distance", (0, 3), W);
  label(scale(.85)*"time", (4, 0), S);
  dot((1.25, 4.5));
  label(scale(.85)*"Evelyn", (1.25, 4.8), N);
  dot((2.5, 2.2));
  label(scale(.85)*"Briana", (2.5, 2.2), S);
  dot((4.25,5.2));
  label(scale(.85)*"Carla", (4.25, 5.2), SE);
  dot((5.6, 2.8));
  label(scale(.85)*"Debra", (5.6, 2.8), N);
  dot((6.8, 1.4));
  label(scale(.85)*"Angela", (6.8, 1.4), E);
  [/asy]
  Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
  <|im_start|>assistant
  
prompt.role: user
extra_info.answer: \text{Evelyn}
extra_info.question: The results of a cross-country team's training run are graphed below. Which student has the greatest average speed? [asy]
  for ( int i = 1; i <= 7; ++i )
  {
  
  draw((i,0)--(i,6));
  }
  
  for ( int i = 1; i <= 5; ++i )
  {
  
  draw((0,i)--(8,i));
  }
  draw((-0.5,0)--(8,0), linewidth(1));
  draw((0,-0.5)--(0,6), linewidth(1));
  label("$O$", (0,0), SW);
  label(scale(.85)*rotate(90)*"distance", (0, 3), W);
  label(scale(.85)*"time", (4, 0), S);
  dot((1.25, 4.5));
  label(scale(.85)*"Evelyn", (1.25, 4.8), N);
  dot((2.5, 2.2));
  label(scale(.85)*"Briana", (2.5, 2.2), S);
  dot((4.25,5.2));
  label(scale(.85)*"Carla", (4.25, 5.2), SE);
  dot((5.6, 2.8));
  label(scale(.85)*"Debra", (5.6, 2.8), N);
  dot((6.8, 1.4));
  label(scale(.85)*"Angela", (6.8, 1.4), E);
  [/asy]
extra_info.split: test