What rule relates the amount of milk to the amount of water? it's not d because i got that wrong. so it's either

a) multiply the amount of milk by 4
b) multiply the amount of milk by 2
c)multiply the amount of milk by 1/2

The answer is A) multiply the amount of milk by four.
You can see/check this by taking a value of milk, like 3 tablespoons and multiplying it by four (3 x 4 = 12) and if the point that corresponds with the 3 tablespoons of milk also goes with the 12 tablespoons of water, it works. 

The answer should be A. If You have 4 tablespoons of milk multiply by 4 you get 16 which is the same amount as the water

It will take him 5 days