/ survive / we / work / start / cleaner / safer / energy / sources / A. We won’t survive otherwise we start working on cleaner, safer sources of energy.   B. We won’t survive so we start wo

We won’t survive otherwise we start working on cleaner, safer sources of energy.

We won’t survive so we start working on cleaner, safer sources of energy.

We won’t survive unless we start working on cleaner, safer sources of energy.

We won’t survive although we start working on cleaner, safer sources of energy.