Question: 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

Correct Answer: B
Explanation: “The period… has been established by carbon-14 dating, but what is much more difficult to determine is the reason for their decoration,...” - Correct. The singular noun “The period” used in this answer choice is correctly placed with the singular verb phrase “has been established”. Furthermore, the singular verb “is” used in this answer choice to modify the singular noun “reason”. Moreover, the answer choice uses the verb form “has been established” in the present perfect tense in the correct way. It is used to indicate the action that occurred in the past but continues to impact the present. Additionally, there lies no redundancy or awkwardness in this answer choice. Therefore, option B is the correct answer since it satisfies the rules of grammar. Let’s examine the other given options:

Option A
“The period…has been established by carbon-14 dating, but what is much more difficult to determine are the reason for their decoration,...”- Incorrect. The plural verb form “are” is used incorrectly in this answer choice to indicate the singular noun “the reason”. The sentence must use the singular verb form “is” to refer to the singular noun “the reason” in order to make the sentence correct. Hence, option A is the incorrect answer choice since it does not satisfy the rules of grammar. Thus option A gets eliminated.

Option C
“The period…have been established by carbon-14 dating, but what is much more difficult to determine is the reason for their decoration,...”- Incorrect. In this answer choice, the singular noun “The period” is incorrectly placed with the plural verb phrase “have been established”. It is required to remember that the singular verb is always used to refer to a singular noun form. The verb phrase should be “has been established” in order to make the}
sentence correct. Hence option C is the incorrect answer since it does not satisfy the rules of grammar. Thus, option C gets eliminated.

Option D
“The period…have been established by carbon-14 dating, but what is much more difficult to determine are the reason for their decoration,...” - Incorrect. The singular noun “The period” used in this answer choice is incorrectly placed with the plural verb phrase “have been established”. It is required to remember that the singular verb is always used to refer to a singular noun form. The verb phrase should be “has been established” in order to make the sentence correct. Moreover, the plural verb form “are” is used incorrectly in this answer choice to indicate the singular noun “the reason”. The sentence must use the singular verb form “is” to refer to the singular noun “the reason” in order to make the sentence correct. Hence option D is the incorrect answer since it does not satisfy the rules of grammar. Thus, option D gets eliminated.

Option E
“The period…are established by carbon-14 dating, but that which is much more difficult to determine is the reason for their decoration,...” - Incorrect. The simple present tense “are” is incorrectly used in this answer choice to indicate an action that occurred in the past but continues to impact the present. It is required to note that the present perfect tense “has/have” is used to refer to actions that occurred in the past but have an impact on the present. Moreover, answer choice E depicts a statement that is needlessly wordy. The phrase “but that which is” leads to redundancy and awkwardness in the sentence. Hence, option E is the incorrect answer since it does not satisfy the rules of grammar. Thus, option E gets eliminated.

“The period when the great painted caves at Lascaux and Altamira”- is a GMAT sentence correction question of the GMAT exam. These sorts of questions consist of grammatical errors in the underlined part of the sentence. The candidates need to verify the subject-verb agreement, noun and tenses in the sentence. The candidates must examine the awkwardness and redundancy in the sentence to determine the correct answer by applying logical concepts or ideas. The candidates need to choose the correct statement given in the options. The GMAT sentence correction section requires adequate grammar skills since the candidate has to identify common grammatical errors. GMAT sentence correction is a part of GMAT verbal.

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