1
.
Diana
Northup
has
curiosity
.
She
wants
to
know
about
life
in
this
cave
.
That
means
the
cave
____________________
____________________
____________________
(
must
/
visited
)
.
Caves
are
dangerous
places
,
and
some
risk
____________________
____________________
____________________
____________________
(
have
to
/
taken
)
.
Northup
is
always
careful
.
2
.
She
knows
the
dangers
.
For
example
,
Northup
knows
that
the
air
in
this
cave
is
poisonous
,
so
she
uses
a
gas
mask
.
The
cave
____________________
____________________
____________________
(
mustn't
/
enter
)
without
a
gas
mask
.
3
.
Northup
knows
that
the
level
of
gas
goes
up
and
down
.
When
it
goes
up
,
it
is
extremely
dangerous
.
That's
why
a
gas
meter
____________________
____________________
____________________
____________________
(
have
to
/
use
)
.
With
this
,
the
gas
level
____________________
____________________
____________________
(
can
/
checked
)
while
she
is
down
there
.