Answer:
C
Explanation:
What's happening in the real world?
As he cooks on the barbecue, the weight of the tank goes down because some of the propane is getting used up.
Given that is happening, the graph showing that has to start with a lot in it and slowly decrease.
A shows the exact opposite. As he cooks, he gets more weight in the tank, not less.
B says that over time, there is no change in weight of the tank. How can that be? The tank ought to get lighter. The answer is not B
C is the correct answer.