The S.I unit of velocity is m/s and since it's velocity it needs to be in a particular direction, therefore most appropriate answer is :
B. She is running west at 2.4 m/s
You would want to include qualitative and quantitative evidence
-- The first thing I do when I wake up is go STRAIGHT to the bathroom. Up to that time, my displacement is equal to distance I traveled from my bed.
-- Once I'm relaxed and back in my room, dithering around and getting dressed, the distance I've traveled since I woke up is growing and growing, but my displacement is staying pretty steady, because I'm still hanging right around my bed.
-- I walk to school, walk between classes, maybe run around the track a couple times, walk to the lunchroom and back to classes, then walk home. By dinner time, my distance traveled during the day might be 3 or 4 MILES, but my displacement is only one floor down from my bedroom to the kitchen.
-- After my homework is done, I slide back into my warm bed and turn out the light. My displacement for the day is now zero ! The straight-line distance from the place I started to the place I finished is zero.
It sounds like a special relativity question but I need more info for a total answer. But remember it's length in the lab frame is
L•sqrt(1-(v/c)^2) where L is the rest length, v is its velocity magnitude and c is the speed of light. Sqrt is the square root (I'm on a phone so I can't see the math equation editor)
