The table shows how three cell phone companies charge for minutes.
Cell Phone Plan Comparison
Company Number of Minutes per Month
100 200 500 1200
Mobile Plus $20 $30 $40 $50
Cellular Prime $10 $20 $50 $60
Nation Mobile $5 $10 $25 $60
For which company or companies is there a proportional relationship between the number of minutes and the monthly cost?
A
Mobile Plus only
B
Nation Mobile only
С.
Nation Mobile and Cellular Prime