The period when the great painted caves at Lascaux and Altamira were occupied by Upper Paleolithic people has been established by carbon-14 dating, but what is much more difficult to determine are the reason for their decoration, the use to which primitive people put the caves, and the meaning of the magnificently depicted animals.
(A) has been established by carbon-14 dating, but what is much more difficult to determine are
(B) has been established by carbon-14 dating, but what is much more difficult to determine is
(C) have been established by carbon-14 dating, but what is much more difficult to determine is
(D) have been established by carbon-14 dating, but what is much more difficult to determine are
(E) are established by carbon-14 dating, but that which is much more difficult to determine is

source: GMAT Prep

I am not able to figure out what will be the subject of second clause..?
according the Manhattan SC Guide, I tried flipping the clause..
...but what is much more difficult to determine are the reason for their decoration, the use to which primitive people put the caves, and the meaning of the magnificently depicted animals.


he reason for their decoration, the use to which primitive people put the caves, and the meaning of the magnificently depicted animals are what is much more difficult to determine ?

The only reason i can think of is...

the construction of the sentence is
The period.......people has been established, but what .....is the reason for X , Y & Z.

So Two singular clauses in parallel. In 1st clause it is very clear that The period...can't be plural so we need a singular clause after but. And the Noun clause are anyways always singular.

Also as MGMAT SC guide says when in doubt think singular.

Using the spits we are down to A or B.

I took the cue from "the reason" highlighted in blue above and chose B

As I can break it down:
1. For the first subject-verb agreement, it "The period" + "has/have" - so it eliminates C, D, & E.
2. The subject is "the reason for their decoration" and hence verb must be singular.

So for me the answer choice is 'B'.

well i feel Sunny.jain is correct in his flipping the clause strategy.

Think it this way: What is much more difficult to determine are three things A,B and C say the reason, the use and the meaning.
A, B anc C together make a compound subject.
Hence i feel ARE is more appropriate than IS

This Question is from OG verbal (1st edition) so no doubt OA is B, may be Instructors can comment more.

hi -

this is really important:

if anything BEFORE the verb CAN BE the subject, then that thing will be the subject.

this advice mostly applies to sentences like this one: "A is/are B".
specifically:
in the sentence "noun1 is/are noun2", noun1 is the subject.
in the sentence "noun2 is/are noun1", noun2 is the subject.

for instance:
the hardest part of the test was the last three questions --> "hardest part" is the subject.
the last three questions were the hardest part of the test --> "last three questions" is the subject.

you only have a backward construction (verb before subject) if NOTHING in FRONT of the verb is eligible to be the subject.

on the table are two cell phones
--> "on the table " is a prep. phrase and therefore can't be the subject, so this is a backward construction. "two cell phones" is the subject.

harder than anything else on the test were the last three questions
--> here "harder than anything on the test" contains no eligible subjects, so this is backward construction; "the last three questions" is the subject.

Hello Ron,

What will be the subject in the above option B?

Thanks in advance!

The Sub here is
What is much more difficult to determine.

As per Manhattan SC guide this is called Sub Phrase and it is always singular.

Correct me if I am wrong.

Ron, Your explanations are amazing.

correct.

to other readers - this poster is talking about the subject of the SECOND clause (the clause that follows "comma + BUT").
the subject of the first clause is, rather more obviously, "the period".

Thanks Ron!

glad it helped

Thank you Ron and Poonam! :)

Hello Ron,

I got another doubt.

In your earlier post in this thread you said->

harder than anything else on the test were the last three questions
--> here "harder than anything on the test" contains no eligible subjects, so this is backward construction; "the last three questions" is the subject.

Why can't "harder than anything on the test" be the singular noun phrase?

Plz do explain.

Thanks in advance!

Hi Ron,

Can you please help me understand my question above?

Thank you