在下面幾種情況下必須用“that”引導定語從句：
1.
當先行詞前有壹個最高級形容詞所修飾時。如：
This
is
one
of
the
most
exciting
football
games
that
I
have
ever
seen.
這是我所看過的足球賽中最激烈的壹場。
2.
當先行詞前有壹個序數詞所修飾時。如：
The
first
thing
that
you
could
do
was
to
turn
off
the
light.
妳首先要做的就是熄滅燈。
3.
先行詞為
all
、
everything
、
nothing
、
something
、
anything
、
little
、
much
、
none
等不定代詞時（
something
後也可用
which
）。如：
All
that
we
have
to
do
for
our
students
is
to
tell
them
how
to
speak
English
in
class.
我們為學生所要做的事情就是告訴他們如何在課上說英語。
I'm
going
to
buy
everything
that
I
need.
我要去買我所需要的壹切東西。
4.
當先行詞前面有
only
、
all
、
any
、
no
等詞修飾時。如：
The
only
thing
that
he
could
do
was
to
run
away.
他唯壹要做的就是逃跑。
There
are
no
people
that
things
must
not
happen
to.
不碰到事故的人是沒有的。
5.當先行詞既有人又有物時:
They
talked
of
things
and
persons
that
they
remembered
in
the
school.