Error Spotting – Choose the segment (A–D) that contains a grammatical error; select “No error” only if the entire sentence is correct. Sentence: A) One of the most effective B) solutions is that C) she should work on Sunday D) and complete the assignment.

Introduction / Context:
This question tests the idiomatic completion of a predicate after a singular head subject, and whether a finite “that-clause” or a non-finite “for + pronoun + to-infinitive” structure is preferable. Many competitive exams target the common error “is that she should …” where the idiomatic and concise construction is “is for her to …”.

Given Data / Assumptions:

• Subject head: “One” (singular) from the phrase “One of the most effective solutions”.
• Predicate in B–D currently reads: “is that she should work on Sunday and complete the assignment”.
• Intended meaning: recommending the best course of action for “her”.

Concept / Approach:
When recommending or prescribing an action, English typically favors the “for + objective pronoun + to-infinitive” structure after a linking verb: “The best solution is for her to work …”. A “that-clause” is not always wrong, but here it is wordy and unidiomatic for a recommendation. Exams therefore flag “is that” as the error trigger in this context.

Step-by-Step Solution:
1) Identify the copular predicate after the singular head “One … is …”.2) Inspect complement choice: “that she should work …” (finite clause) vs “for her to work …” (non-finite, idiomatic for advice/plan).3) Prefer idiomatic structure: “One of the most effective solutions is for her to work on Sunday and complete the assignment.”4) Therefore, the erroneous portion is B: “solutions is that”.

Verification / Alternative check:
Paraphrase with other nouns of recommendation: “The best way is for her to …”, “The ideal plan is for her to …”. Each naturally uses “for + pronoun + to-infinitive”.

Why Other Options Are Wrong:

• A: Correct introductory segment of a partitive NP.
• C: “she should work on Sunday” is fine once the complement type is fixed.
• D: Parallel verb “complete” aligns with “work”.

Common Pitfalls:
Assuming any “that-clause” is acceptable after “is …”; ignoring idiomatic preference in prescriptive statements; overlooking the head noun “One” for agreement.

Final Answer:
Option B