Answer:
Time (week 1 - week 10)
Step-by-step explanation:
Given
Measure of cost of gasoline over a period of time
Required
Determine what variable belongs to the horizontal axis
To answer this question, I'll re-echo the given parameters again
Measure of cost of gasoline over a period of time
This can be rephrased to be
Measure of cost of gasoline with respect to time
This means that the cost of gasoline is a function of time (10 weeks, to be precise).
Hence;
Cost will be on the vertical axis
Time will be on the horizontal axis
Conclusively,
The first option answers the question