____________________
materials
are
obtained
directly
from
____________________
.
Raw
materials
are
prepared
or
refined
to
obtain
____________________
materials
.
By
processing
natural
materials
,
we
can
obtain
other
types
of
materials
.
These
materials
are
called
____________________
materials
.
Technical
materials
can
be
both
____________________
or
processe
d