i think its d! hope that helps! is that flvs?
Graph A its the beat answer
In the old aquarium, 3 tablespoons of salt were used for 20 gallons. That's a conversion ratio of

That is, for every gallon of water in the aquarium, there was 0.15 tbsp of salt. So a 50 gallon aquarium, Ill should add

to maintain the salinity.