In the following sentence about education and power, identify which part contains a grammatical error: Education is a instrument which (1) imparts knowledge and, therefore (2) indirectly controls power. (3) No error (4).

Introduction / Context:
This question examines a basic but extremely important feature of English grammar: the correct use of articles a and an before singular countable nouns. Error spotting items like this are common because they quickly reveal whether a learner has mastered foundational rules. You need to determine which labelled segment of the sentence contains an error, or whether the sentence is free from grammatical mistakes.

Given Data / Assumptions:

• Part (1): Education is a instrument which.
• Part (2): imparts knowledge and, therefore.
• Part (3): indirectly controls power.
• Part (4): No error.
• The noun "instrument" begins with a vowel sound.
• Standard article usage rules apply.

Concept / Approach:
In English, the indefinite article "a" is used before words beginning with a consonant sound, while "an" is used before words beginning with a vowel sound. The noun "instrument" begins with the vowel sound "i", so the correct form is "an instrument". Using "a instrument" breaks this phonetic rule. The rest of the sentence uses a defining relative clause and a compound predicate to describe what education does, and these portions are grammatically correct.

Step-by-Step Solution:
Step 1: Look at part (1): "Education is a instrument which". Step 2: Identify the article noun combination "a instrument" and recall that "instrument" starts with a vowel sound. Step 3: Apply the rule that "an" precedes vowel sounds, so the phrase should be "an instrument". Step 4: Check part (2): "imparts knowledge and, therefore". This correctly continues the clause and uses a proper linker "therefore". Step 5: Check part (3): "indirectly controls power." This is a correct verb phrase completing the idea. Step 6: Since no other obvious grammatical problems exist, the only error is in part (1).

Verification / Alternative check:
Rewrite the corrected sentence: "Education is an instrument which imparts knowledge and, therefore, indirectly controls power." This version sounds natural and maintains the original meaning while respecting article usage. The phrase "an instrument which imparts knowledge" is a standard relative clause construction. There is no need to change any other part of the sentence, which confirms that the problem is limited to the article in part (1).

Why Other Options Are Wrong:
Part (2) is grammatically sound; it uses "imparts knowledge" correctly and places "therefore" in a reasonable position. Part (3) is also correct, as "indirectly controls power" clearly describes one effect of education. Part (4) cannot be correct because we have identified a definite article error earlier in the sentence. Thus, parts (2), (3), and (4) should not be chosen as the answer.

Common Pitfalls:
Many learners mistakenly focus on written spelling rather than spoken sound when choosing "a" versus "an". For example, they may misapply the rule when a word begins with a consonant letter but a vowel sound, or vice versa. In this case, "instrument" clearly starts with a vowel sound and must pair with "an". Practising with sets of examples like "an apple", "an instrument", "a book", and "a university" helps fix this rule by linking it to sound rather than spelling alone.

Final Answer:
The error is in Part (1), where "a instrument" should be corrected to "an instrument".