Which statement best explains how the conditions identified in Part A affect the availability of opal?
A
Weathering processes no longer occur in Australia, so no new opal is formed.
B
Gems do not need an exact combination of elements or minerals to form, so opal forms more easily.
C
Opal formation occurs over large periods of time, so the number of opal deposits is limited.
D
Volcanoes in Australia no longer provide high temperatures and pressures, so no new opal is formed.