In this English error spotting question, identify the part that contains the error in: "It has been shown that (A) very high doses of vitamin C actually (B) causes cancer cells to grow. (C) No Error (D).".

Introduction / Context:
This error spotting question focuses on subject verb agreement in a scientific style sentence. The sentence given is: "It has been shown that (A) very high doses of vitamin C actually (B) causes cancer cells to grow. (C) No Error (D)." You must decide which segment contains the disagreement between the subject and the verb.

Given Data / Assumptions:

• Full sentence: "It has been shown that very high doses of vitamin C actually causes cancer cells to grow."
• Part (A): "It has been shown that"
• Part (B): "very high doses of vitamin C actually"
• Part (C): "causes cancer cells to grow."
• Part (D): "No Error"
• The true grammatical subject of the verb in part (C) is "very high doses of vitamin C", which is plural because of "doses".

Concept / Approach:
Subject verb agreement requires that a plural subject take a plural verb, and a singular subject take a singular verb. Here, the clause after "that" is "very high doses of vitamin C actually cause cancer cells to grow." The head noun "doses" is plural. Therefore, the verb should be "cause", not "causes". The introductory "It has been shown that" is a dummy subject construction and does not affect the internal agreement in the subordinate clause. Hence the error lies where the singular verb form "causes" is used instead of the plural form "cause".

Step-by-Step Solution:
Step 1: Identify the clause after "that": "very high doses of vitamin C actually causes cancer cells to grow."Step 2: Determine the true subject of this clause: "very high doses of vitamin C".Step 3: Recognise that "doses" is plural, and the phrase "very high doses of vitamin C" should be treated as a plural noun phrase.Step 4: Apply the rule: plural subject → base form verb without s; singular subject → verb with s in the simple present.Step 5: Replace "causes" with "cause" so that the corrected sentence reads: "It has been shown that very high doses of vitamin C actually cause cancer cells to grow."

Verification / Alternative check:
The introductory clause "It has been shown that" is in present perfect passive and is correct. The adverb "actually" is correctly placed to emphasise the unexpected nature of the result. The object "cancer cells" and the infinitive phrase "to grow" are also correct. Only the verb "causes" is mismatched. Once you change it to "cause", the subordinate clause becomes grammatically complete. Therefore, the error must be located in part (C), where the verb appears.

Why Other Options Are Wrong:

• Option A (part A "It has been shown that") is a correct reporting structure for research findings and requires no change.
• Option B (part B "very high doses of vitamin C actually") correctly introduces the subject and an adverb, with proper placement and word choice.
• Option D (No Error) is incorrect because the subject verb agreement is clearly violated in part (C).

Common Pitfalls:
Students sometimes get distracted by the proximity of the singular noun "vitamin C" and wrongly match the verb with that instead of the true head noun "doses". In noun phrases with "of", always identify the head word before "of" to determine number: "dose of vitamin C" (singular) versus "doses of vitamin C" (plural). Matching the verb with the wrong noun in such phrases is a very common exam trap.

Final Answer:
The error is in part C, where "causes" should be corrected to "cause" to agree with the plural subject "very high doses of vitamin C".