The "eight glasses a day" rule presumes 8-oz glasses:
8 x 8 = 64 oz = 2 quarts
1 quart = 946 ml x 2 = 1892 ml
So you should drink 3.784 of those 500ml bottles of water.
Looked at another way, each of those 8oz glasses of water holds 236.5 ml, so if you drink all four 500ml bottles of water, you're drinking a little more than 8 1/2 glasses of water.
Looked at a third way, if you measure an extra half-ounce of water into each of your eight glasses, you're up to four 500ml bottles.
To make sure you are prepared for every outcome so if in the future if something goes unplanned you already somewhat expected it
D would make the most money, but it's up to you! :)
