English Grammar — Spot the error (choose the incorrect part; select 'No error' if the sentence is correct). Sentence parts: A) Your machine would not have B) given you so much trouble C) if you had D) maintained it proper. E) No error

Introduction / Context:
In error-spotting questions for English grammar, the sentence is split into parts. Your task is to identify the part that violates standard usage. This item tests adverb vs. adjective choice after a verb like “maintain,” and the idiomatic collocation used to describe the manner of maintenance.

Given Data / Assumptions:

• The sentence is a third conditional: “would not have … if you had …”
• Segment D reads “maintained it proper.”
• Standard English prefers an adverb “properly” after a verb to modify the action.

Concept / Approach:
Adjectives modify nouns, while adverbs modify verbs, adjectives, or other adverbs. After an action verb like “maintained,” the word describing the manner of maintaining must be an adverb. Therefore, “properly” is required, not “proper.”

Step-by-Step Solution:

Verification / Alternative check:
Substitute a synonymous adverb such as “correctly” to confirm the pattern: “maintained it correctly” fits; hence “properly” is the right form.

Why Other Options Are Wrong:

• A: Grammatically fine for a conditional result.
• B: Natural collocation “so much trouble.”
• C: Correct past perfect trigger in third conditional.
• E: Not applicable because D contains an error.

Common Pitfalls:
Confusing adjective/adverb forms (proper vs. properly) and overlooking collocations after verbs. Learners sometimes accept “maintained it proper” due to colloquial influence, but it is non-standard in formal English.

Final Answer:
D) maintained it proper.