Answer: The first diagram.
Step-by-step explanation: In order for a mapping diagram to be a function, there needs to be 1 x value assigned to 1 value. if we look at the first image provided, this is not the case. Notice that 3 has two arrows going to different numbers which are 6 and 7. Since this makes it's difficult to make predictions about data from this, we would call this not a function.
