Respuesta :

A) Does any graph show a proportional relationship?
  Yes, the graph for Tank B.

B)
The number of gallons at the 1 minute mark is 300. The "unit rate" is
  300 gal/min

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The graph of a proportional relation is a straight line through the origin. That of Tank A has a non-zero y-intercept, so is not a proportional relation. The graph of Tank B is a proportional relation.