knewton problem-can anybody explain

The link is broken...

sir full question posted

The exact year when the Mogao caves in Dunhuang, China began to be sculpted and chiseled by the Northern Wei Dynasty has been difficult to verify, but what is much easier to determine are the purpose of their existence, the religious significance that the drawings on the walls of the caves held, and the order in which the caves were constructed.

(A) has been difficult to verify, but what is much easier to determine are
(B) has been difficult to verify, but what is much easier to determine is

(C) have been difficult to verify, but what is much easier to determine is
(D) have been difficult to verify, but what is much easier to determine are
(E) are difficult to verify, but that which is much easier to determine is


IMO: B ( but in question the underlined and should be or)
In C, D, E year is singular so it cannot be have or are

pradeepkaushal9518 wrote:sorry i dont know why link is not working . i have posted the question. i dont hv the oa/OE

https://gmatmania.com/Gmattopic_Detail.aspx?topicid=13


knewton

The exact year when the Mogao caves in Dunhuang, China began to be sculpted and chiseled by the Northern Wei Dynasty has been difficult to verify, but what is much easier to determine are the purpose of their existence, the religious significance that the drawings on the walls of the caves held, and the order in which the caves were constructed.



(A) has been difficult to verify, but what is much easier to determine are
(B) has been difficult to verify, but what is much easier to determine is

(C) have been difficult to verify, but what is much easier to determine is
(D) have been difficult to verify, but what is much easier to determine are
(E) are difficult to verify, but that which is much easier to determine is

The answer should be A

The year (singular) --> has

What is easier to determine? - the purpose, the religious significane and the order (plural) are

let us wait for experts reply

Hi Pradeep,

Found the same post posted by you some 3 years back, and that too along with the expert comments..
Just FYR ..

https://www.beatthegmat.com/knewton-vr-4-t66917.html

good actually that time i was having knewton online course i have the question saved but didnt have the answers.