Uranium-235 has a half- life of 710 million years. If it is determined that a certain amount of stored U-235 will be considered safe for a particular storage area only when its radioactivity has dropped below 0.1% of the original level. Approximately how much time will this be

According to the passage, which of these is true about gray water systems? a) gray water systems use plants that require less water. eliminate b) gray water systems require the use of less fossil fuels. c) gray water systems reduce the amount of fresh water used. d) gray water systems reduce the amount water used by shower heads.