You discover a unicellular organism that moves by what appear to be pseudopodia. You conclude that this organism is .

either a type of amoeba or a type of slime mold

Explanation:

Based on the description provided you would most likely conclude that this organism is either a type of amoeba or a type of slime mold. That is because these are the most common types of unicellular organisms that move by temporarily protruding an arm-like projection of a eukaryotic cell membrane in order to travel in the direction that it is protruding that member from its cell membrane. This form of movement can be seen in the picture below.

well, that's easy; the answer's c, "it reduces contamination of the water and substrate of the estuary."