In this English grammar error spotting question, the sentence is divided into three labelled parts followed by a No error option. You must decide which part of the sentence contains a grammatical mistake. The sentence is: During the class (A) the teacher request to (B) the students to have patience. (C) If you think there is no mistake, you would choose option (D) No error.

Introduction / Context:
This question checks your understanding of subject verb agreement and correct verb patterns in English. The sentence describes a teacher speaking to students during a class and asking them to be patient. Examinations often break such sentences into labelled parts so that you can focus on one segment at a time. Your job is to identify which specific part contains the grammatical error or to decide that the entire sentence is correct. Here, the problem is connected with the verb form request and how it should be used with the subject the teacher and with its object.

Given Data / Assumptions:

• The sentence is presented as During the class (A) the teacher request to (B) the students to have patience. (C)
• Part (D) represents the option No error.
• The subject in the main clause is the teacher, which is singular.
• The time frame is general and refers to what happens during the class.
• The sentence intends to express that the teacher asked the students to have patience.

Concept / Approach:
Two rules are important here. First, in the simple present tense, a singular subject like the teacher takes a verb with s or es, for example the teacher requests. Second, the verb request is normally followed directly by an object and then an infinitive, as in requested the students to wait, or by that plus a clause, as in requested that the students wait. The phrase request to is not idiomatic in this context when followed by a direct object. Therefore, part (B) must be corrected both for subject verb agreement and for the unnecessary preposition to.

Step-by-Step Solution:
Step 1: Check part (A) During the class. This is a correct prepositional phrase that sets the time context and does not contain any grammatical error. Step 2: Examine part (B) the teacher request to. The subject the teacher is singular and should take a verb with s in the simple present, so request should become requests or, in a different tense, requested. Step 3: Notice that the phrase request to is awkward in this structure. The natural pattern is requested the students to have patience or requests the students to have patience. Step 4: Check part (C) the students to have patience. This phrase correctly acts as the object and infinitive complement, and it would fit smoothly after a correctly formed verb phrase requested or requests the students to have patience. Step 5: Combine the corrected pieces to verify the sentence: During the class, the teacher requested the students to have patience. This reads correctly and naturally. Step 6: Since the error lies only in the wording of part (B), the correct option is Part (B) the teacher request to.

Verification / Alternative check:
You can also check the sentence by trying an alternative grammar pattern with that. For example, During the class, the teacher requested that the students have patience is also correct. In both correct versions, the verb is requested and there is no preposition to directly after request. This confirms that the core problem is in the verb form and extra preposition in part (B).

Why Other Options Are Wrong:
Part (A) is only a time phrase and is completely acceptable as During the class.
Part (C) the students to have patience is correct when it is attached to the correct verb phrase requested, so it does not contain any error by itself.
Part (D) No error is wrong because we have clearly identified that part (B) contains a mistake that needs correction.

Common Pitfalls:
A common pitfall in such questions is that candidates may only look for tense errors and miss subject verb agreement in singular subjects with third person present tense verbs. Another frequent error is to assume that adding prepositions like to will make a phrase sound more formal, when in fact it can make the verb pattern incorrect. Remember that request someone to do something is correct, while request to someone in this structure is not. Carefully checking verb forms and standard patterns will help you avoid these traps in similar questions.

Final Answer:
The error is in part (B) because the phrase should be the teacher requested the students to have patience instead of the teacher request to the students to have patience. Therefore the correct choice is Part (B) the teacher request to.