36
.
Before
the
use
of
bricks
,
the
Great
Wall
was
mainly
built
from
stones
,
wood
and
____________________
____________________
.
37
.
Many
western
sections
of
the
wall
are
constructed
from
mud
and
thus
are
more
____________________
____________________
____________________
.
38
.
A
part
of
the
wall
in
Gansu
province
may
disappear
in
the
next
20
years
,
due
to
____________________
____________________
.
39
.
To
see
the
wall
from
the
Moon
would
require
superhuman
____________________
.
40
.
The
Great
Wall
is
generally
recognized
as
one
of
the
most
impressive
____________________
____________________
in
history
.
