Answer:

The correct answer is option 'D' - Policeman.

Explanation:

Helpers at School:
- A school has various helpers who play different roles to ensure the smooth functioning of the institution and the safety of the students.

Policeman:
- A policeman is a law enforcement officer who maintains law and order in society and ensures the safety and security of the people.
- While a policeman is an important helper in the community, they are not directly involved in the day-to-day activities of a school.
- Their primary responsibility is to maintain law and order in the entire area they are assigned to, rather than being specifically dedicated to a single school.

Other Options:
a) Watchman:
- A watchman is responsible for guarding the school premises and ensuring its security.
- They monitor the entry and exit of individuals, keep an eye on the surroundings, and report any suspicious activities.
- Their presence helps to create a safe environment for students and staff.

b) Teacher:
- Teachers are the main educators and mentors in a school.
- They impart knowledge, guide students in their academic and personal growth, and create a positive learning environment.
- Teachers play a crucial role in shaping the future of students.

c) Gardener:
- A gardener is responsible for maintaining the school garden and outdoor areas.
- They take care of plants, trees, and the overall cleanliness of the garden.
- Gardening adds beauty to the school premises and provides a conducive environment for students.

Conclusion:
- While all the other options (watchman, teacher, and gardener) are helpers commonly found in schools, the presence of a policeman is not a typical feature of a school setting.
- Policemen are responsible for maintaining law and order in the community as a whole, rather than being exclusively associated with a school.