Which element is always found in impure form

a. copper
b. nitrogen
c. hydrogen

kindly answer as fast as possible : )

Which object forms when a supergiant runs out of fuel? a red giant a black hole a white dwarf a neutron star

What approach is required to balance the objectives of sustainable development? balancing the objectives of sustainable development requires a(n) .

When svante arrhenius first proposed his acid-base theory, he was a doctoral candidate. his professors thought his ideas were unfounded. within a decade, the arrhenius theory of acid-base was widely accepted and praised within the scientific world. arrhenius defined acids as compounds having ionizable hydrogen and bases as compounds with ionizable a) barium. b) hydronium. c) hydroxide. d) oxygen.