如何判断一个句子是宾语从句还是定语从句还是名词性从句

顾名思意，修饰宾语的从句是宾语从句，如：I
know
a
person
who
is
very
kindly.
person在主句当中作宾语，后面who引导的从句是宾语从句
定语从句的主要作用
是修饰限定主语，如，He
that
is
carelss
forgot
to
turn
off
the
light
that
is
careless
修饰he，引导的是定语从句
名词性从句字的是可以充当名词的从句或者是起到名词作用的从句，如，who
was
speaking
loudly
will
stand
all
day
long!

1.
I
think
that
it
is
important
to
learn
English.这个句子含有一个名词性从句，在句中作think的宾语，因此that
it
is
important
to
learn
English就是宾语从句。

2.
This
is
the
book
whose
cover
is
red.这个句子含有一个修饰名词the
book的从句，且作定语，因此whose
cover
is
red就是定语从句。

宾语从句就是整个从句做宾语，如I
don't
know
what
is
right.
句中
what
is
right就是宾语从句。
定语从句就是整个从句做定语，修饰一个名词。
如I
don't
know
the
boy
who
is
very
homesome.句中who
is
very
homesome是修饰the
boy
的。