第1个回答 2019-10-22
when，while，as引导时间状语从句的区别
when，while，as显然都可以引导时间状语从句，但用法区别非常大。
一、when可以和延续性动词连用，也可以和短暂性动词连用；而while和as只能和延续性动词连用。
①
Why
do
you
want
a
new
job
when
youve
got
such
a
good
one
already？（get为短暂性动词）你已经找到如此好的工作，为何还想再找新的？
②Sorry，I
was
out
when
you
called
me．（call为短暂性动词）对不起，你打电话时我刚好外出了。
③Strike
while
the
iron
is
hot．（is为延续性动词，表示一种持续的状态）趁热打铁。
④
The
students
took
notes
as
they
listened．（listen为延续性动词）学生们边听课边做笔记。
二、when从句的谓语动词可以在主句谓语动作之前、之后或同时发生；while和as从句的谓语动作必须是和主句谓语动作同时发生。
1．从句动作在主句动作前发生，只用
when。
①When
he
had
finished
his
homework，he
took
a
short
rest．（finished先发生）当他完成作业后，他休息了一会儿。
②When
I
got
to
the
airport，the
guests
had
left．（got
to后发生）当我赶到飞机场时，客人们已经离开了。
2．从句动作和主句动作同时发生，且从句动作为延续性动词时，when，while，as都可使用。
①When
／While
／As
we
were
dancing，a
stranger
came
in．（dance为延续性动词）当我们跳舞时，一位陌生人走了进来。
②When
／While
／As
she
was
making
a
phonecall，I
was
writing
a
letter．（make为延续性动词）当她在打电话时，我正在写信。
3．当主句、从句动作同时进行，从句动作的时间概念淡化，而主要表示主句动作发生的背景或条件时，只能用
as。这时，as常表示“随着……”；“一边……，一边……”之意。
①
As
the
time
went
on，the
weather
got
worse．（as表示“随着……”之意）
②
The
atmosphere
gets
thinner
and
thinner
as
the
height
increases．随着高度的增加，大气越来越稀薄。
③As
years
go
by，China
is
getting
stronger
and
richer．随着时间一年一年过去，中国变得越来越富强了。
④The
little
girls
sang
as
they
went．小姑娘们一边走，一边唱。
⑤The
sad
mother
sat
on
the
roadside，shouting
as
she
was
crying．伤心的妈妈坐在路边，边哭边叫。
4．在将来时从句中，常用when，且从句须用一般时代替将来时。
①You
shall
borrow
the
book
when
I
have
finished
reading
it．在我读完这本书后，你可以借阅。
②When
the
manager
comes
here
for
a
visit
next
week，Ill
talk
with
him
about
this．下周，经理来这参观时，我会和他谈谈此事。
三、when用于表示“一……就……”的句型中（指过去的事情）。
sb．had
hardly（＝scarcely）
done
sth．when．．．＝Hardly
／
Scarcely
had
sb．done
sth．when．．．
①I
had
hardly
／scarcely
closed
my
eyes
when
someone
knocked
at
the
door．＝Hardly
／
Scarcely
had
I
closed
my
eyes
when
someone
knocked
at
the
door．我刚一闭上眼，就有人在敲门了。
②I
had
hardly
／scarcely
entered
my
room
when
the
telephone
rang．＝Hardly
／Scarcely
had
I
entered
my
room
when
the
telephone
rang．我刚一走进房门，电话就响了。