The methods proposed for reducing the amount of interest to be paid are not able to be used successfully without creating a problem of insufficient cash flow in the future.

"Are not able to be" is a mouthful. "Cannot" is better. This rules out A and B...."successfully to be used" is also not correct. "Without succeeding in" isn't the same meaning. C remains.

A) are not able to be used successfully without creating a problem of insufficient cash flow in the future

B) are not able successfully to be used without creating a problem in the future of insufficient cash flow

C) cannot successfully be used without creating a future problem of insufficient cash flow

D) cannot be used without succeeding in creating a problem in the future of insufficient cash flow

E) cannot be used without succeeding in creating a future problem of insufficient cash flow
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Subject of the sentence is "Methods"

Options A & B suggest Methods are not able... which isnt' right

Option D & E correct the above error but mention "cannot be used without succeeding in creating a problem ". This changes them meaning of orginial sentience. Original sentence says Methods can't be successfully used where as Options D &E convey successfully creating a problem

Option E corrects the errors and conveys right meaning of sentence

What is verb of the sentence “cannot successfully be used without creating a future problem of insufficient cash flow”
cannot be used....?

"can" can say about qualification or a possibility. inhere, we need to say about a possibility, so, "we can use "can" as in choice C, D and E.

"able" is used to say about qualification not about a possibility, so, choice A and B is incorrect.

Rahaman9969 , yes, cannot be used is the verb.

Methods . . . cannot be used [successfully] . . . without creating a problem.

You are correct.
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Is there a difference between “cannot successfully be used” and “cannot be used successfully”? Are both these constructions grammatically correct?
I had selected A just because it had used the latter one and “cannot successfully be used” seemed wrong to me.

Posted from my mobile device

In a situation in which we have to "connect" the used to something, I'd probably prefer the option that puts successfully next to can.

Neither method can be used successfully to do something.

Neither method can successfully be used to do something.

But this question doesn't test us on that, so the better answer to your question is that both those phrases are possible. Just keep in mind that option A uses are not able to be used successfully, not cannot be used successfully. That is, we are not asked to take that call in this question.
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The methods proposed for reducing the amount of interest to be paid are not able to be used successfully without creating a problem of insufficient cash flow in the future.


A) are not able to be used successfully without creating a problem of insufficient cash flow in the future

B) are not able successfully to be used without creating a problem in the future of insufficient cash flow

C) cannot successfully be used without creating a future problem of insufficient cash flow - looks good

D) cannot be used without succeeding in creating a problem in the future of insufficient cash flow -

E) cannot be used without succeeding in creating a future problem of insufficient cash flow

A) are not able to be used successfully without creating a problem of insufficient cash flow in the future
(1) meaning error: “The methods…are not able to be used successfully…” how can “methods” be able to do anything? Illogical;

B) are not able successfully to be used without creating a problem in the future of insufficient cash flow
(1) meaning error: “The methods…are not able successfully…” how can “methods” be able to do anything? Illogical; (2)

C) cannot successfully be used without creating a future problem of insufficient cash flow
Best option

D) cannot be used without succeeding in creating a problem in the future of insufficient cash flow
(1) meaning error: “The methods…cannot be used WITHOUT SUCCEEDING IN CREATING A PROBLEM…” so the methods can’t be used UNLESS there is success in the creation of a problem, particularly around the future of insufficient cash flow? Illogical and changes the meaning

E) cannot be used without succeeding in creating a future problem of insufficient cash flow
(1) meaning error: similar to that of option D