将句子变成被动语态

Question

1 How many desks do they buy every term? 2 We must tie the young tree to the stick. 将句子变成被动语态,每空一词 3 You needn't do it now. It___ ___ ___ by you now. 4 People use metal for making machies. Metal___ ___ for making machies. 5.He made me do that for him . I___ ___ ____that for him. 6 Did they buld a birdge here a year ago? ___a bridge __here by them a year ago?(把6第一句改为陈述句的时候，here 应该防在哪里，为什么) 还有，麻烦把每一句的答案后都做解释，我希望能够真正知道原因。谢谢。麻烦了！

Answer 1

1、How
many
desks
are
bought
by
them
every
term?
这是一般现在时的被动语态：am、is、are
+
过去分词（+
by
sb.)
2、The
young
tree
must
be
tied
to
the
stick
by
us.
这是情态动词被动语态：情态动词+
be
+
过去分词（+
by
sb.)
3、You
needn't
do
it
now.
It
need
not
done
by
you
now.(同样是情态动词的被动语态）
4、People
use
metal
for
making
machies.
Metal
is
used
for
making
machies.(一般现在时被动语态)
(现在be
used
for
(doing)
sth.已经成为固定短语了）
5、He
made
me
do
that
for
him.
I
was
made
to
do
that
for
him.一般过去时的被动语态：was、were
+
过去分词（+
by
sb.）
注意：感官动词以及一些使役动词（如：have、make、let等）后面可以接宾语补足语是动词不定式的复合宾语（即宾语加宾语补足语）结构，主动语态中不定式不带to,但被动语态中不定式中的to不能省略。
6、Did
they
buld
a
birdge
here
a
year
ago?
Was
a
bridge
built
here
by
them
a
year
ago？
如果改为陈述句应该是：They
built
a
bridge
here
a
year
ago.因为时间状语要放在地点状语之后。