In this English grammar error detection question, identify the part of the sentence "Every effect we see, hear or speak in our outside or physical world has a specific cause that have its origin in the inner or mental world" which contains a grammatical mistake.

Introduction / Context:
This sentence expresses a philosophical idea about cause and effect, but the exam focuses on subject verb agreement and correct auxiliary usage. The sentence reads Every effect we see, hear or speak in our outside or physical world has a specific cause that have its origin in the inner or mental world. The general meaning is acceptable, but there is a grammatical problem related to the verb phrase that have its origin.

Given Data / Assumptions:
- The subject in the main clause is Every effect, which is singular. - The main verb is has a specific cause. - A relative clause follows: that have its origin in the inner or mental world. - Only one part of the sentence contains an error.

Concept / Approach:
The relative pronoun that in the clause that have its origin refers back to the singular noun cause. Therefore, the verb in this relative clause must also be singular, which means has, not have. The phrase its origin further confirms that the writer sees the cause as a singular entity. When subject and verb disagreement occurs in such structures, exams expect you to detect the mismatch. The incorrect plural auxiliary have appears in part 3 of the sentence division.

Step-by-Step Solution:
Step 1: Identify the noun that the relative pronoun that refers to. It refers to cause in the phrase a specific cause. Step 2: Recognise that cause is a singular noun, because it is preceded by a, indicating one specific cause. Step 3: Observe the verb in the relative clause: have its origin. Step 4: Note that have is the plural form, while the singular form for third person is has. Step 5: See that the phrase its origin also shows the singular nature of the subject. Step 6: Conclude that the correct form should be has its origin, so the error lies in the part that currently uses have.

Verification / Alternative check:
We can rewrite the sentence as: Every effect we see, hear or speak in our outside or physical world has a specific cause that has its origin in the inner or mental world. This corrected version reads smoothly and maintains singular subject verb agreement throughout. As another check, if we changed the noun to causes, the relative clause would change to that have their origin. Since the sentence uses the singular cause and its, the matching auxiliary must be has, not have. Thus part 3 contains the error.

Why Other Options Are Wrong:
Option A is wrong as an answer because the phrase Every effect we see, hear or speak in our outside is awkward but not grammatically incorrect in terms of agreement. Option B is wrong because or physical world has a specific cause that is structurally sound and continues the thought correctly. Option D is wrong because the sentence is not error free; the auxiliary verb in the relative clause must be corrected.

Common Pitfalls:
Long sentences with relative clauses and several verbs can easily confuse learners. They might incorrectly match have with the nearest plural seeming word, such as effects, and forget that the relative pronoun connects to cause. A useful technique is to isolate the relative clause and read it with its noun: the cause has its origin. This reveals the correct form. Regular practice with sentences that include that, which, and who can strengthen your ability to track subject verb agreement across complex structures.

Final Answer:
The correct answer is Part 3: "have its origin in the inner or mental world."