In his search for an effective method of motivating his

Is the in option D) "was" is not required. Is it a typo?

I rejected the Option D) based on the "was".

Why does the "was" come after the second clause? Is that alright?

correct idiom is ' the more ... the greater '
options A,B and C are out
option E changes the meaning by use of ' advanced preparation ' thus making it a incorrect answer choice
correct answer - D

willing ness to do
is idiomatic
willingness for doing has different meaning.
my willingness to learn english for good future is good.

increase more is correct, increase greater is not correct.

e is wrong

the more - the greater - correct idiom
A/B/C - are out right away.

D) the greater their willingness to prepare themselves in advance was
looks good.

E) the greater their willingness for advanced preparation increased
changes the meaning - advanced preparation is different from prepare themselves in advance.

clearly D is more appropriate.

I saw this question on Kaplan's portal.
Option D is a bit different from what has been given here.
Please find the question below ,

In his search for an effective method of motivating his students to practice, the piano teacher found that the more he reminded his students of their possible embarrassment in the upcoming recital, their willingness to prepare themselves in advance increased.

A. their willingness to prepare themselves in advance increased

B. their willingness to be prepared in advance was increasing

C. their willingness for advanced preparation was greater

D. the greater their willingness became to prepare themselves in advance

E. the greater their willingness for advanced preparation increased

Yes, I think its a Typo. If not then its the most incorrect choice. How can a sentence end in "was"! Its silly.

(D) is the correct answer.

The idiom here is "the [MORE/GREATER] X ... the [MORE/GREATER] Y." In this case, the more the teacher reminded his students, the greater their willingness was.

(A) does not correctly employ the idiom, instead simply using the verb "increased."

(B) uses the wrong verb form of "increase" and fails to use the correct idiom.

(C) does not correctly use the idiom; "the greater" should follow the comma after "recital."

(D) is the correct answer.

(E) incorrectly matches "greater" with "increased." Something cannot increase greater; rather, something increases more

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