Answer: Es peligroso comer peces de los lagos de Nicaragua porque el agua esta contaminada.
Explanation: the question is:
What sentence is not true about Nicaragua?
The sentences are:
It is dangerous to eat fish from the lakes of Nicaragua because the water is contaminated.
There is proof of the natives walking on the coast of Lake Managua.
The Nicaragua lake is the biggest one, has wildlife of the Caribean sea.
The only option false here is the first one, you actually can eat fish from the Nicaragua lakes, while it may be contaminated, it is a fountain of work and food for lots of people.
Then the right option is:
Es peligroso comer peces de los lagos de Nicaragua porque el agua esta contaminada.