In the proverb based sentence "Still waters run deep", determine whether any part of the sentence contains an error or whether it is error free.

Introduction / Context:
This question uses the well known English proverb Still waters run deep. Error spotting with proverbs checks whether the learner recognises standard expressions that should not be altered. We need to decide if any part of the sentence has a grammatical error or if the proverb is used correctly as it stands.

Given Data / Assumptions:

The sentence is split into parts: Still (A), waters (B), run deep (C), and No Error (D).

Still waters run deep is a fixed proverb in English.

The proverb means quiet or calm people often have very strong feelings or deep thoughts.

The grammatical subject is waters, which is plural.

The verb is run, which agrees with the plural subject.

Concept / Approach:
Proverbs and idiomatic expressions often follow set patterns. Still waters run deep is one such idiom. Grammatically, still functions as an adjective meaning calm or motionless, modifying the plural noun waters. The verb run matches the plural noun, and deep is an adverbial complement describing how the waters run. There is no error in any part of this proverb.

Step-by-Step Solution:
Step 1: Check part A. Still correctly works as an adjective before waters, meaning calm. Step 2: Check part B. Waters is a plural noun often used in poetic or literary expressions for stretches of water. Step 3: Check part C. Run deep is a verb phrase describing the behaviour of water; the verb run is plural and matches waters. Step 4: Confirm that the proverb as a whole is standard and appears in dictionaries and phrase books. Step 5: Conclude that there is no grammatical or idiomatic error.

Verification / Alternative check:
Compare the sentence with common reference sources or recall that this exact expression is frequently used without any change. Attempting to alter it, for example to still water runs deep, would change both the grammar and the accepted wording. Since proverbs are generally memorised in fixed form, matching the known form confirms that the sentence is correct.

Why Other Options Are Wrong:
Option A is wrong because still is correctly placed and correctly used as an adjective here. Option B is wrong because waters is a valid plural noun used in literary expressions about rivers, seas and lakes. Option C is wrong because the plural verb run correctly agrees with waters and deep functions correctly as a complement. Option E is irrelevant since part D contains only the label for the no error option.

Common Pitfalls:
Some learners misinterpret still as an adverb of time, expecting a different structure. Others may think that water cannot be pluralised in formal English, but waters is standard in poetic or descriptive contexts. Remember that idioms and proverbs often preserve older forms and should be learned as complete units.

Final Answer:
The proverb is correct as written, so The sentence has no error in any part. is the correct choice.