Question

what is the main difference between red tides and algae blooms, aside from their color?
a. red tides are not caused by algae
b. red tides produce harmful toxins
c. algae blooms occur only in ponds or lakes
d. algae blooms do not affect plants and animals

Explanation:

Red tides are a type of harmful algal bloom (HAB) caused by toxin-producing dinoflagellates (a type of algae), so A is wrong. Algal blooms can occur in marine and freshwater environments, so C is wrong. Algal blooms (including non-toxic ones) can deplete oxygen and harm aquatic life, so D is wrong. The key difference (aside from color) is that red tides produce harmful toxins, making B correct.

Answer:

B. Red tides produce harmful toxins