Answer: 3
Explanation:
The black widow, the hobo spider, and the brown recluse spider are all poisonous. They all have lethal venom.
Human activity can affect the river ecosystems because first of all humans take the water and use it for themselves, they also pollute it, disturb the ecosystems and kill fish or oysters etc. in the ecosystems.
20 is the Number of Neutrons of potassium.
