Question

HELLLLLLLLLLP MEEEEEEEE PLS

THIS QUESTION IS NOT HARD BUT MY BRAIN DOESNT GET IT.
the last answer choice is blocked but it says
0 only sample 4​

Answer 1

Answer:

3 and 4

Explanation:

Both appear to be up river which mean they're coming DOWN to contaminate the uptake. If they're ahead of the uptake facility they're not going to show up in the water. I only know this because of City Skylines :)