What is true about the mass of protons and neutrons?
a) they are exactly equal to each other.
b) they are exactly equal to 1 amu.
c) they have negligible mass.
d) they have masses slightly greater than 1 amu.

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.