Answer: a. 20 drops to 4 cups
Explanation:-
Five drops of medication to 1 cup of water means the ration of medication to water is 5: 1.
a. a. 20 drops to 4 cups
Ratio will be

b. 10 drops to 1 1/2 cups
Ratio will be

c. 15 drops to 2 cups
Ratio will be

d. 2 drops 1/2 cup
Ratio will be

Thus five drops of medication to 1 cup of water is the same as 20 drops to 4 cups .Answer: a. 20 drops to 4 cups