necessary

to

complete

the

design

before

National

Day？

a.this

b.that

c.it

d.he

C should be chosen in this question, and the other items are disturbing to some extent. This paper mainly investigates the usage of the formal subject it

. Generally speaking, when the subject is a complex component (such as infinitive, gerund, clause, etc.), the formal subject it is usually used at the beginning of the sentence, and the real subject is put behind:

is

it

necessary

to

tell

his

father

everything. Is it necessary to tell his father all this?

it

is

wrong

to

say

anything

like

that

on

that

occupation. It is wrong to say that on that occasion.

it's

no

good

sitting

up

too

late. It's no good staying up late.

it'll

be

wonderful

lying

on

the

beach

all

day. How wonderful it would be to lie on the beach all day!

it

is

quit

clear

that

he

has

read

the

book. Obviously, he has read this book.

it's

a

problem

where

we

could

get

so

much

money

. It's a difficult problem where we can get so much money.

sometimes the preposition for/of

can be added before the infinitive used as the subject:

it

is

very

kind

of

you

to

say

that. It's very kind of you to say so. It

is

important

for

us

to

keep

the

balance

of

nature. It is very important for us to keep the ecological balance.