Choose the correct answer:
 
1. Four students were asked to represent the same motion on paper.

Student A drew a horizontal position–time graph.
Student B drew a straight sloping position–time graph.
Student C drew a velocity–time graph with an upward slope.
Student D drew a velocity–time graph parallel to the time axis.
Only one student has represented an object that is not changing its position.
Who is correct?
 
2. A student records the position of a moving object every second. Another student records only the object's speed at one exact moment.
Which statement best explains why the two observations cannot always be compared directly?