a large number of、a lot of、plenty of、a great many有什么区别？

a
large
number
of
表示许多的，只能修饰可数名词；a
lot
of等于lots
of，即可修饰可数的，又可修饰不可数名词；plenty
of也是修饰可数或不可数名词，与a
lot
of同义但不如其常用；a
great
many只能修饰可数名词,等于a
good
many。记住这些在使用时就不会混淆了。例句：
1、A
large
number
of
high-tec
products
have(has)
been
made
in
that
factory(那个工厂生产了许多高科技产品）a
number
of做主语时，动词可用单数，也可用复数。
2、Don't
hurry.
We
still
have
plenty
of
time.
There
are
plenty
of
such
persons
in
our
school.可数和不可数都可以。
3、He
got
a
lot
of(lots
of)homework(things)to
do
after
school.可数和不可数都可以。
4、They
raised
a
great
many(a
good
many)proposals
at
the
meeting.只能是可数的。
此外，表示大量，许多的还有a
large
quantity
of，修饰可数和不可数名词，如：
As
a
result
of
destroying
the
forests,
a
large
quantity
of
desert
has
coverd
the
land(毁林导致了大量土地的荒漠化）.
On
that
day
she
received
a
large
quantity
of
flowers.