1. If the emission of CO2 **continues** at high rate, the climate **will be destroyed**.
2. If the air **is not** clean, the breathing problems **will be reduced**.
3. We **will save** the trees if we **save**.
4. If schools **teach** about environmental problems, all students **will know** how to protect the environment.
5. What **will you do** if you **are** President?
6. If I **owned** a lonely island, I **would build** a huge house by the beach.