When the isotonic saline solution described in part A is connected to an unknown solution via a semipermeable membrane, the unknown solution level drops. Based on this information, what can be said about these two solutions?
A) The two solutions have the same concentration.
B) The unknown solution had the lower concentration.
C) The unknown solution had the higher concentration.

B. The unknown solution had the lower concentration.

Explanation:

Osmosis is a phenomenon in which the molecules of the solvent has a tendency to move through a membrane which is semipermeable from lower concentrated side to the higher concentration side, so that the concentrations on both sides of the membrane must be equal.

So the unknown solution may have lesser concentration than the isotonic solution so that molecules of that solution move from less concentrated side to the more concentrated side, so its level drops.

the answer is c. nacl