Directions: Each sentence is divided into four parts, which may or may not contain an error. Choose the section that has the error as your answer choice. If all sections are correct, choose "No error" as your answer.

Complicated disputes are frequently escalate (A) / to a state supreme court, which can (B) / deliver judgments that establish guidelines (C) / for lower courts under its authority (D).

The correct answer choice is A.

Explanation:
Section (A) contains a grammatical error related to verb forms and sentence structure.

1. Error Analysis in Section (A):
The phrase in section (A) reads: "Complicated disputes are frequently escalate".
Here, the auxiliary verb "are" is incorrectly combined with the base form of the verb "escalate".

2. Grammatical Rule:
When a form of the verb "to be" (is, am, are, was, were) is used as an auxiliary verb with a main verb:
- In active voice (continuous tense), it must be followed by a present participle (verb + -ing), e.g., "are escalating".
- In passive voice, it must be followed by a past participle (verb + -ed), e.g., "are escalated".
- If simple present tense in active voice is intended, the auxiliary verb "are" is not required at all, e.g., "frequently escalate".

3. Correct Form of Sentence:
The sentence can be fixed in one of two ways:
- "Complicated disputes frequently escalate to a state supreme court..." (Simple Present Tense / Active Voice)
- "Complicated disputes are frequently escalated to a state supreme court..." (Passive Voice)

4. Verification of Other Sections:
- Section (B): "to a state supreme court, which can" — Uses the relative pronoun "which" correctly to refer back to "a state supreme court", followed by modal verb "can".
- Section (C): "deliver judgments that establish guidelines" — Uses the base verb "deliver" after modal "can", followed by a relative clause ("that establish...") correctly agreeing with the plural noun "judgments".
- Section (D): "for lower courts under its authority" — Grammatically sound prepositional phrase where singular possessive pronoun "its" correctly refers to the state supreme court.