Answer:
1. No dudo que más del 90 por ciento de nuestros ríos estén contaminados.
2. Es posible que los peces dejen de existir para el año 2050.
3. No es seguro que la energía nuclear sea la solución para el siglo XXI.
4. Es verdad que mueran millones de vacas por una enfermedad misteriosa.
5. Es imposible que una señora de 67 años tenga bebé.
6. Niego que el reciclaje contamine más de lo que ayuda al planeta.
Explanation:
To express doubt, possibility or certain negations, the subjunctive form of the verbs in question is used.
The subjunctive mode is one of the three verbal modes that exist along with the indicative mode and the imperative mode.
For example:
In the sentence number 2 change the verb dejar for dejen which is the subjunctive form of the verb.
The subjunctive is the mode of unreality, expresses desire and possibility:
Example:
Maybe I go on vacation to Mexico.
Tal vez vaya de vacaciones a Mexico
In the subordinate sentences the subjunctive appears:
They are subordinate sentences introduced by Que.
The subjunctive is used in subordinate sentences with denial: I don't think you think that (que) like for example all the sentences in this exercise use que to introduce the subjunctive.
