All life relies on a relatively narrow range of ph, or acidity.
Acids have low ph's.
All life relies on a relatively narrow range of low phs.
All life relies on a relatively narrow range of what?
Options:
(1) voltage
(2) Energy
(3) sun's heat
(4) low pHs
(5) Decibels
(6) spectrum
(7) Light
(8) sunlight