B c and d are not pure substances.
A. Snails and crayfish would not survive in Birch Lake at a pH of 6.2.
B. Once they die out, the walleye will disappear as well.
Walleye: pH 6.0 — pH 9.0
Crayfish: pH 6.5 — pH 8.0
Snails: pH 6.4 — pH 8.0
At pH = 7.3, all three can survive.
At pH = 6.2, snails and crayfish will die out.
Then, the walleye will disappear because <em>their food supply has vanished</em>.
