Sentence Correction

Declining revenues resulting from a decrease in business travel, a source of income without which most commercial airlines could not survive, are going to force many commercial airlines to increase prices and decrease services in the coming months.
(A) a source of income without which most commercial airlines could not survive, are
(B) a source of income without which most commercial airlines could not survive, is
(C) and most commercial airlines use it as a source of income to survive with, are
(D) which is a source of income which is needed by most commercial airlines who could not survive without it, are
(E) which most commercial airlines use as a source of income without which they are unable to survive, is

in a) and b) i wonder how Declining revenues could the source of income.

can someone explain the subject of the sentence?

ashish1354 wrote:Declining revenues resulting from a decrease in business travel, a source of income without which most commercial airlines could not survive, are going to force many commercial airlines to increase prices and decrease services in the coming months.
(A) a source of income without which most commercial airlines could not survive, are
(B) a source of income without which most commercial airlines could not survive, is
(C) and most commercial airlines use it as a source of income to survive with, are
(D) which is a source of income which is needed by most commercial airlines who could not survive without it, are
(E) which most commercial airlines use as a source of income without which they are unable to survive, is

in a) and b) i wonder how Declining revenues could the source of income.

can someone explain the subject of the sentence?

Hi Ashish,
Declining revenues is not the source of income. Business travel is source of income.
Let me explain it by breaking the sentence.
First of all, the parts between "," can be removed because they are non-essential modifiers.
Let us consider that the initial sentence was this:
Declining revenues resulting from a decrease in business travel are going to force many commercial airlines to increase prices and decrease services in the coming months.
Now you can clearly see that the subject is Declining revenues as you have already pointed out.

Now, let us modify this sentence to make the meaning clear. Author wants to put some information about "business travel" to make the sentence more clear and author puts some non-essential information between commas after "business travel"
And the sentence becomes:
Declining revenues resulting from a decrease in business travel, a source of income without which most commercial airlines could not survive, are going to force many commercial airlines to increase prices and decrease services in the coming months.
So now it is clear that the part between "," is modifying "business travel" and not declining revenues.
Please let me know if this helps.