Complete with the present or fucture simple form of the verb .
1. If we ( continue ) flying so much , global warming (get) worse
2. People (not stop ) flying until train travel ( become ) cheaper
3. When fights ( get ) more expensive , people ( use ) other means of transport .
4. Governments ( have ) to work togethewr if they (want) to reduce carbon emissions .
5.There ( be) serious climate change unless we (take) action soon .