Unit 4
Don’t eat in class.
祈使句
1.
定义。
用来表达命令、请求、劝告、警告、禁止等的句子叫作祈使句。祈使句通常省略主语
you
。例如
:
Be quiet,please.
请安静。
Please have a seat.
请坐。
2.
句式结构。
( 1 )Do
型
:
动词原形
+
宾语
+
其他。例如
:
Go this way,please.
请这边走。
( 2 )Be
型
:Be+
表语
+
其他。例如
:
Be a good kid!
做个好孩子
!
( 3 )Let
型
:Let+
宾语
+
动词原形
+
其他。例如
:
Let me help you.
让我来帮你。
注意
:
祈使句的否定形式一般是在动词原形前加
don
’
t
构成
,
有时也可直接用
no
开头表示禁止。例如
:
Don
’
t be late for school!
上学不要迟到
!
No smoking!
禁止吸烟
!
have
to
与
must
的用法
have to
和
must
均可表示
“
必须
”
。
must
更加强调说话者的主观意愿
;
而
have to
强调客观的必要性
,
意为
“
不得不
”
。两者的否定式含义大不相同。
mustn
’
t
表示
“
不准
;
禁止
”,
而
don
’
t have to
表示
“
不必
”
。例如
:
I must go now,or I
’
ll be late.
我现在必须走了
,
不然我就会迟到了。
She has to help her mother look after her sister.
她不得不帮着她妈妈照顾妹妹。
You mustn
’
t swim in the river.
你不准在河里游泳。
You don
’
t have to do it now.
你现在不必做这件事。
注意
:
以
must
开头的一般疑问句
,
其肯定回答用
must,
否定回答用
needn
’
t
或
don
’
t have to
。例如
:
—Must I finish the work now?
我现在必须完成这项工作吗
?
—Yes,you must./No,you don
’
t have to.
是的
,
你必须完成。
/
不
,
你不必现在完成。
Ⅰ
.
根据句意用所给词的适当形式填空
1.
Do
( do ) the work right now,Jim.
2.Please
tell
( tell ) me the news.
3.Let
’
s
play
( play ) soccer now.
4.You must
come
( come ) to school on time.
5.No
talking
( talk ) here!
Ⅱ
.
根据句意用
must
或
have
to
的适当形式填空
1.You
must
do it yourself.
2.—
Must
I read the book in the reading room?
—No,you
don
’
t have to
.
3.It
’
s late.Jim
has to
go home.
4.—
Must
Lily keep quiet?
—Yes,she
must
.
5.You don
’
t
have to
get up early on weekends.
Ⅲ
.
按要求完成句子
,
每空一词
1.You can
’
t listen to music when your mother is sleeping.(
改为祈使句
)
Don
’
t
listen
to music when your mother is sleeping.
2.He has to be in bed by ten o
’
clock.(
改为一般疑问句
)
Does
he
have
to be in bed by ten o
’
clock?
3.You must come here early this afternoon.(
改为祈使句
)
Come
here early this afternoon.
4.Let her help you.(
改为否定句
)
Don
’
t
let
her help you.
5.She has to ride her bike to go home.(
改为否定句
)
She
doesn
’
t
have
to
ride her bike to go home.
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