Water is formed when two hydrogen atoms bond to an oxygen atom.

when a substance is made of two or more atoms like this, we call it
a) a mixture.
b) a complex.
c) a compound.
d) an element.

Why are scientists concerned about the depletion of the ozone levels in the stratosphere?

How much time has elapsed from the very beginning of "the memior of the conquistador bernal diaz del castillo" to the end? a. castillo's whole life b. a quarter of an hour c. a few weeks d. a decade

Si units are the modern form of the