If there isn’t enough rain, the hydropower station cannot operate. A.  When there isn’t enough rain, the hydropower station can operate. B.  Unless there is enough rain, the hydropower stat

When there isn’t enough rain, the hydropower station can operate.

Unless there is enough rain, the hydropower station can operate.

Unless there isn’t enough rain, the hydropower station cannot operate.

Unless there is enough rain, the hydropower station can’t operate.