Depending
on
their
____________________
metals
can
be
classified
into
:
.
-
____________________
.
Its
main
____________________
is
____________________
.
They
are
____________________
,
____________________
and
____________________
____________________
.
.
-
____________________
.
They
____________________
____________________
____________________
or
just
a
little
.
Examples
:
____________________
,
____________________
,
____________________
,
____________________
.