The concept of curriculum includes:

The concept of curriculum is multifaceted and encompasses more than just the formal plan.

• The official curriculum refers to the explicit, planned learning experiences and subjects.
• The hidden curriculum includes the unstated norms, values, and beliefs transmitted through the school environment and social interactions.
• The observed curriculum represents what is actually taught and learned in practice, which may differ from the official plan.

Therefore, a comprehensive understanding of curriculum includes all these dimensions, making 'All of the above' the correct answer. Options A, B, and C individually represent only partial aspects of the broader curriculum concept.