A student did an experiment with two identical fish tanks, Tank 1 and Tank 2. About 10 mL water purifier was added to Tank 1. The water purity of each tank was tested every day in particles per liter. The purity was recorded over a period of 5 weeks in the table shown below.

Week Water Purity of Tank 1 Water Purity of Tank 2
1 12.6 12.6
2 12.6 13.9
3 13.9 14.4
4 14.7 15.8
5 15.6 17.6


Based on the table, which of these conclusions is correct?

> Adding water purifier keeps fish tanks clearer for longer.
> Fish tanks need less than 10 mL of water purifier to stay clear.
> Fish need 10 mL of water purifier to survive.
> Water purifier can help a fish survive longer.