f
is
a
connective
preposition
that
takes
____________________
a
clause
as
its
____________________
.
(
Some
shorter
forms
exist
:
I'll
call
you
____________________
necessary
.
)
The
if
structure
is
not
a
clause
but
a
prepositional
phrase
[
if
+
clause
]
.
In
a
____________________
/
future
____________________
statement
,
an
if
phrase
expresses
a
single
occurrence
of
a
situation
that
is
required
for
the
acitivity
in
the
main
clause
to
occur
.
(
If
X
,
then
Y
)
The
speaker
is
uncertain
whether
the
____________________
in
the
if
phrase
____________________
occur
or
not
.
The
____________________
____________________
tense
is
____________________
in
the
clause
after
if
,
and
a
modal
(
will
,
can
,
may
,
might
,
shall
)
is
____________________
in
the
main
clause
.
The
meaning
is
"
Under
the
condition
that
X
occurs
,
Y
____________________
happen
.
