Explanation:

The correct answer is option 'C' which states that "a student must maintain their marks throughout the year". Let's break down the sentence to understand why option 'C' is the correct choice.

Subject:
The subject of the sentence is "a student". This refers to an unspecified student, implying that it applies to any student in general.

Verb:
The verb in the sentence is "must study". This implies that the action of studying is necessary or obligatory for the student.

Object:
The object in the sentence is "hard". This describes the manner or intensity with which the student must study.

Complement:
The complement in the sentence is "to maintain their marks throughout the year". This provides additional information about the purpose or result of studying hard. It indicates that the student needs to study hard in order to maintain their marks consistently over the entire year.

Explanation:
Studying hard is essential for students to maintain their marks throughout the year. By consistently putting in effort and dedicating time to their studies, students can ensure that they perform well in their exams and assignments. Maintaining good marks throughout the year is important as it reflects a student's understanding of the subject matter and their ability to consistently apply themselves. It also sets a strong foundation for future academic success.

Regular studying and revision help students to reinforce their knowledge and retain information for longer periods. It allows them to stay on top of their coursework and ensures that they are well-prepared for assessments. Consistency in studying also helps to reduce stress and anxiety that may arise from last-minute cramming or incomplete understanding of the material.

Moreover, maintaining good marks throughout the year can have positive effects on a student's overall academic performance. It can contribute to higher grades, increased self-confidence, and a sense of accomplishment. It can also open up opportunities for scholarships, college admissions, and future career prospects.

In conclusion, studying hard is crucial for students to maintain their marks throughout the year. By consistently investing time and effort into their studies, students can achieve academic success, build a strong foundation of knowledge, and set themselves up for future achievements.