Answer:
Trend line (Best fit line).
Step-by-step explanation:
In scatter plots the trend line gives the best approximation of the data. The approximation is of a linear equation. With this line it can be easy to estimate more values for a given x value. The graph here shows the distance covered in the corresponding time. The trend line here is a function of distance and time.
So, the name of the part of the graph labeled 7 is the Trend line (Best fit line).